Cooking Under Pressure: Pressure Caramelized Sweet Potato Soup

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Just in time for winter, we decided to develop a new seasonal variation of one of our Modernist Cuisine traditions: Pressure Caramelized Sweet Potato Soup. The recipe for this magical soup incorporates black peppercorns to give it a nice zip, and hints of sweet onion and Makrud leaves complement the caramelized sweet potato stock.

 

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The charm of this soup is twofold: the elevated temperature of pressure-cooking coupled with an alkaline environment ensure that caramelization reactions will flourish.

Vegetables are made up of cells with strong walls that soften at higher temperatures than the cells in meat do. Vegetables are composed mostly of water, however, and their temperature normally won’t exceed the boiling point of water (100˚C/212˚F) until they are dried out. Vegetables in a fully pressurized cooker don’t dry out as they quickly become tender under higher temperatures (120˚C/250˚F). And because the air is sealed in, you don’t need to add much water, so juices are extracted without becoming diluted.

Add to this a pinch of baking soda to bring the soup to a more alkaline pH of about 7.5 and you have ideal conditions for Maillard reactions to commence. The result is a gorgeously colored soup that is the concentrated essence of caramelized sweet potato.

 

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We like to finish our soup with purple sweet potato confit, roasted chestnuts, and toasted marshmallows. The purple sweet potatoes add a brilliant dash of color, and toasted marshmallows add a touch of tradition and whimsy. This soup is the perfect way to begin special dinners this holiday season.

Pressure-Caramelized Sweet Potato Soup

Mastering creamy pureed potatoes, no fat required

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When made just right, mashed potatoes are the ultimate comfort food: smooth, creamy, warm and filling — not to mention a perfect vehicle for gravy.

But how to get them perfectly smooth and creamy? Too often ridding mashed potatoes of those pesky lumps forces you to overwork the spuds into a gummy, grainy mess. Or you end up adding so much cream and butter that the dairy drowns out the flavor of the potatoes.

If you like your mashed potatoes fluffy, the answer is fairly straightforward. Choose a floury variety of potato, such as Maris Piper or russet, pass the peeled, boiled potatoes through a ricer, then mix in just enough butter and milk or cream to moisten.

But if you’re after a silkier texture — more like what the French call pommes puree — stick with waxy potatoes, such as Yukon gold or fingerlings. You also should try a modernist technique pioneered by food writer Jeffrey Steingarten and refined by the British chef Heston Blumenthal. It adds a step, but it is well worth it.

Steingarten discovered that gently heating the potatoes for a half hour or so in warm water before they are boiled profoundly improves the result. This is because as the potatoes soak in water at about 160 F (70 C), the starch in them gelatinizes, producing a smoother puree on the tongue. The granules that contain the starch also firm up, making it harder to rupture them during mashing.

Recently our research chefs perfected yet another modernist method that yields an amazingly smooth and slightly sweet potato puree, and all without adding any butter, milk or cream. The secret is to deploy a little trick of biochemistry that converts the starch in the potatoes into sugar.

The key to this culinary alchemy is an enzyme known as diastase. Don’t let the fancy name put you off; this ingredient is quite natural (it is derived from malted grain), and you can buy it online or at stores that sell brewing and baking ingredients. The enzyme typically is sold in in a ready-to-use form called diastatic malt powder.

Like other enzymes, diastase is a protein whose complex molecular shape allows it to accelerate chemical transformations with amazing speed and specificity. When you eat a starchy food like bread or potatoes, enzymes in your gut help break down the starch into simpler carbohydrates (such as sugars) that your body can burn or store for energy. By adding diastase to our mashed potatoes, we’re simply getting a jump on the process.

The trickiest part about using diastatic malt powder is measuring the right amount. It’s potent stuff, so you really should measure ingredients by weight. After you have peeled and cubed the potatoes, weigh them. For every 100 grams of potatoes, measure out 1 gram of diastatic malt powder. So 1,100 grams of peeled, cubed potatoes calls for 11 grams of malt powder.

Now fill a pot with water and add 2 grams of sugar and 3 grams of salt for every 100 milliliters of water. Simmer the potato cubes until they are tender, 30 to 40 minutes, then drain. Stir the diastatic malt powder into the potatoes, then pass the mixture through a ricer.

The riced potatoes next get sealed in a zip-close plastic bag, which is set in a pot of hot tap water (about 125 F) for a half hour. The warmth activates the enzyme and starts it gobbling up the potato starch. When the 30 minutes is up, empty the bag into a pot, then heat the puree to at least 167 F (75 C) to halt the enzymatic activity.

That’s it. Even with no butter or cream, the result is sweet and amazingly smooth. If you are avoiding dairy or limiting your intake of fats, this technique may just renew your love affair with the potato.

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Click here for our Dairy-Free Potato Puree recipe made with diastatic malt powder.

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Photo credit: Nathan Myhrvold / Modernist Cuisine, LLC.

5 Tips for Culinary Deception

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What better time to trot out our favorite deceptive culinary tricks than April Fool’s Day? We devoted a section of Modernist Cuisine to trompe l’oeil because it is particularly suited to the Modernist movement. Though it has a long history, dating back to dishes such as mock turtle soup in the 19th century, culinary deception has been embraced in recent years by chefs such as Wylie Dufresne, Andoni Luis Aduriz, and René Redzepi.

The key in each of the tips below is to both surprise and delight the senses. There are no malicious tricks here. These tips serve to enhance the senses, present food in creative ways, and keep guests living in the moment. It wouldn’t serve our purposes to develop recipes that don’t taste good!

  1. Raw “Eggs”: One of our favorite culinary tricks to play on visitors to our lab is to convince them that we are serving them a raw quail egg. Anjana Shanker, development chef, who usually whips up this recipe, has gone so far as to make up a story that we discovered a nest of quails on the roof, and started domesticating them for their eggs. In reality, we serve spherified passion fruit and lemongrass in a real quail egg shell. Watch the video above to see what happened when the guys from Tested.com dropped by. Anjana’s technique is included in the video as well.
  2. Mystery Meat: Trompe l’oeil dishes have a long history of substituting one food for another. Besides being just for fun, this is often due to economic reasons (such as mock turtle soup or surimi) or dietary restrictions (as in veggie patties). Sometimes, it can be both! This April Fool’s Day, enlist a vegetarian friend to help play a trick on party guests by casually eating what appears to be meat. Our favorite and most convincing dish is to creating bulgogi out of watermelon, originally designed by Andoni Luis Aduriz at Mugaritz. Cut 2.5 cm / 1 in “steaks” out of seedless watermelon (leave a little bit of the white part of the rind in as a fat cap). Soak the watermelon in a brine (20% water and 1% salt) for two hours. Pat the watermelon dry and dehydrate the slices at 55 °C / 130 °F until dry and leather-like, about 8–12 hours.
  3. Eat Dirt: In the video below, we use chocolate cookies to make fake dirt to go along with our fishing-lure-molded gummy worms. This is the fastest and easiest way to make fake dirt, but in Modernist Cuisine we have a savory version using black bread, chicory root, mushroom powder, and a few other ingredients. We’ve also made fake coals out of cassava roots, simmered with fish stock and squid ink (another recipe inspired by Aduriz).
  4. Impregnated Fruit: Sometimes it’s not the eyes that play tricks, but preconceived notions. When your guest bites into an apple, they expect it to taste like an apple, but by using Modernist techniques, you can impregnate said apple with flavors, such as curry, for a delightful surprise. Vacuum seal a peeled and cored apple with apple juice and spices for 12 hours. Then place the bowl in a chamber vacuum sealer and pull the vacuum three times, holding for 15 minutes the final time. If you don’t have a chamber vacuum sealer, you can also achieve this effect with a whipping siphon. One favorite combination is to infuse celery with apple juice. Place the celery in the siphon, and cover it with apple juice. Then charge with two cartridges of nitrous oxide. Chill it for two hours before serving.
  5. Healthier Substitutes: Sometimes a bit of culinary deception can improve your health. At El Bulli, Feran Adrìa once served grated cauliflower in lieu of couscous. Use a microplane to grate the cauliflower until it is the size of grains. This surprise is especially effective after serving your family real couscous three nights in a row.

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The Secret to the Perfect Soft-Boiled Egg

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A perfect soft-boiled egg is a thing of beauty: a yolk with the texture of sweet condensed milk surrounded by a white that is tender but not runny. But for generations, great cooks have differed on how to achieve this state of perfection reliably.

Some authorities say you should drop a whole egg into boiling water for about three minutes — a bit longer if the egg is extra-large — and then gently peel away the shell. That can leave the yolk too runny, however. And when the egg is peeled, it’s all too easy to tear the tender white into a mess.

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The legendary Julia Child advocated a six-minute boil (for large eggs starting at room temperature, or a minute longer if chilled), followed by a rinse with cold water before and also during peeling. That certainly works for the white, but often overcooks the center.

The French food scientist Hervé This argued some years ago that temperature, not time, is all that matters to the egg—cook it to 65 °C / 149 °F, and the result will be heavenly no matter how long it sits in the water. Or so it was thought. For a while, the “65°C egg” was all the rage at high-end restaurants.

But more recent research by the food chemist Cesar Vega , an editor and coauthor of the 2012 book The Kitchen as Laboratory, conclusively showed that both time and temperature matter. Moreover, the white and the yolk contain different blends of proteins, so the white gels at a higher temperature and a different rate than the yolk does. Vega’s rigorous experiments have armed scientifically inclined chefs with the information they need to cook eggs to whatever texture they like.

When the chefs in our research kitchen make soft-boiled eggs, they use a four step process that involves a blowtorch or liquid nitrogen. Here is a simpler version better suited to the home kitchen. You’ll need a pot of boiling water, a bowl of ice water, a temperature-controlled water bath, and, if you plan on peeling the eggs, a toaster oven.

The first step is to set the egg whites quickly by submerging them completely in a pot of rapidly boiling water for three minutes and 30 seconds, 15-30 seconds less if you like the whites quite loose, as our research chefs do, or 15—30 seconds longer if you prefer the whites fully set. When the time is up, plunge the eggs into the ice water to cool them completely.

Next, cook the yolks to a syrup-like thickness by submerging the eggs in a 64 °C / 147 °F water bath for 35 minutes; it’s important that the water temperature doesn’t change more than a degree or two during cooking. Dry the eggs thoroughly with paper towels. They are now ready to place in egg holders, top, and eat with a spoon. (If you have a Dremel or similar handheld rotary tool, use a thin grinder bit to top the eggs like a pro.)

Alternatively, you can make the eggs easier to peel by drying the shells in a toaster oven. Use a medium-dark toaster setting, and let the eggs heat for two to three minutes to make the shell hot and brittle. It will then readily flake away to reveal a flawless white beneath. Remember to remove the thin skin around the white if it doesn’t come off with the shell.

You can make these eggs in advance and later reheat them in a 60 °C / 140 °F bath for 30 minutes.

By adjusting the temperature of the cooking bath or the time the eggs are in it, you can achieve all kinds of delicious results and reproduce them flawlessly time after time. Prefer a yolk that is more like honey? Let the egg sit in a 65 °C bath for 45 minutes. For a runnier center, try our recipe for Liquid Center Eggs.

Or try cooking them in a 72 °C / 162 °F bath for 35 minutes (you can skip the boiling step). The yolk will then set just firmly enough that you can peel away the white to obtain a perfect yellow sphere, which makes a striking garnish or dumpling-like addition to a soup.

It’s remarkable how advances in science and precision cooking have given new life to this versatile food.

How to Scale a Recipe

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The Mac and Cheese recipe makes five servings, but you’re throwing a dinner party for nine people. You’re in luck: We’ve made it easy to scale our recipes up to greater yields (or down if you have fewer mouths to feed) by using baker’s percentages. Just follow these simple steps.

 

  1. Look in the scaling column of the recipe, and find the ingredient having a scaling value of 100%. Note the weight given. The 100% ingredient is usually the one that has the biggest effect on the yield of the recipe.
    Example: The 100% ingredient in the Mac and Cheese recipe above is white cheddar cheese.
  2. Calculate the scaling factor by dividing the number of servings (or grams) you want to make by the recipe yield.
    Example: This recipe yields five servings. If you are making nine servings, the scaling factor is 9 ÷ 5 = 1.8. (You can use the weight of the yield rather than the servings to calculate the scaling factor: If you want to make 1,100 grams of mac and cheese from a recipe that yields 800 g as written, the scaling factor is 1,100 ÷ 800 = 1.4.)
  3. Calculate the scaled 100% value for the recipe by multiplying the weight of the 100% ingredient by the scaling factor from step 2.
    Example: This five-serving recipe calls for 285 g of white cheddar, which is the 100% ingredient. To make nine servings, you will thus need 285 g x 1.8 = 513.0 g of white cheddar cheese. The scaled 100% value for this recipe is 513.0.
  4. Calculate the scaled weight for every other ingredient in the recipe by multiplying its scaling percentage by the scaled 100% value from above. You can ignore the weights and volumes given in the recipe—just use the scaling percentages.
    Example: The scaling percentage given for dry macaroni is 84%. Multiplying this by the scaled 100% from step 3, you find that 0.84 x 513.0 = 430.9. Similarly, you need 0.93 x 513.0 = 477.1 g of water or milk and 0.04 x 513.0 = 20.5 g of sodium citrate.

Because volume measurements are often rounded to the nearest spoon or cup, you should not multiply or divide volumes when scaling a recipe up or down. Instead, scale the weights as described above, and then weigh the ingredients on a digital scale.

Adapted from Modernist Cuisine at Home

Puffy Snacks You Can Make at Home!

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Everyone loves the crunch of a tasty puffed snack, but we don’t see many of the homemade variety. In our newest video from MDRN KTCHN on CHOW.com, we bring you an easy recipe for puffed rice snacks using your microwave. Watch the video above as our Director of Applied Research, Scott Heimendinger, demonstrates the method and explains how and why it works.

For another slightly more involved recipe for puffed snacks, including tips for puffing success, take a look at our Cheese Puffs recipe in the recipe library, which can also be found in Modernist Cuisine alongside other puffed-food recipes such as crab crackers, chickpeas, and chicken feet. Our new book, Modernist Cuisine at Home includes recipes for puffed pork skin and chicken skin too!

Pizza Trial and Error

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When I set my sights on a topic, I tend to get a little obsessed. This summer, that topic was pizza, and my obsession was in full force. My interest in homemade pizza started with a chapter of the book The Kitchen as Laboratory in which culinary inventor Thomas M. Tongue, Jr. describes a method of leavening pizza dough without yeast by using an encapsulated leavening agent. I was intrigued, so I promptly hunted down a sample of this ingredient and began making pizzas in my home kitchen. As the summer months passed, I logged over 75 pizzas between my oven and my grill, each one a little better than the last. The key breakthrough for me, though, was the discovery that I could substitute flavorful liquids in lieu of water in my pizza dough. After rigorous testing and at least one pizza that self-flambéed (tip: 80-proof rum doesn’t make good pizza dough), I was enamored with champagne pizza dough. In the video from last week, I walk you through the process, which can take as little as 25 minutes from start to finish.

I was also inspired by the many recipes in our new book, Modernist Cuisine at Home, which contains several recipes for pizza dough, sauces, and toppings. We hope they’ll inspire you to experiment on your own as I did.

The Amazing Pressure Cooker

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In the third installment of MDRN KTCHN, our very own Scott Heimendinger and CHOW.com team up to bring you a video all about pressure cooking. Discover how it works, when it was invented, and how baking soda caramelizes root vegetables in 20 minutes.

Now that you can’t wait to dust off your pressure cooker, get the Caramelized Carrot Soup recipe and watch a demonstration by Scott here. Other pressure cooker recipes in our recipe library include Garlic Confit and Vegetable Risotto. For even more recipes using pressure cookers to make everything from stocks to carnitas to marinara sauce, check out our new book, Modernist Cuisine at Home!

Our Favorite Recipes: Roast Chicken

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My favorite dish from Modernist Cuisine at Home is Roast Chicken. Like many people, I grew up eating roast chicken a lot, but having Modernist Cuisine at Home‘s roast chicken is like eating it for the first time. It’s injection-brined and then brushed with soy sauce, which might not be traditional, but these steps act as drying and browning agents for the skin. The result is a chicken that is perfectly moist on the inside and crispy on the outside.

Developmental Chef Aaron Verzosa
Developmental Chef Aaron Verzosa