When we think about innovation in food, we often think about expensive, high-tech gadgets that introduce novel ideas or technologies into our kitchens. The most innovative tools, however, are sometimes the ones that apply traditional techniques in a new way—and they can have the most extraordinary impact on lives. Some of the best ideas are those that solve critical problems.

The piece of equipment that we recently got our hands on falls into the last category. The Wonderbag is a heat-retention slow cooker we find exciting for both its applications in the kitchen and the tremendous effect it’s having on communities around the world. The idea for the cooker came to Sarah Collins, a native of South Africa, during a not-uncommon rolling power outage there. Inspired by memories of her grandmother’s slow-cooking techniques, she decided to continue cooking amid the outage by wrapping hot pots of food in blankets. It was a quick remedy for an immediate problem, but she quickly saw a more important application: power-free cooking could improve conditions in communities that rely on open fires to cook.

Heat-retention cooking is a centuries-old technique that dates back to the middle ages. Food was brought to temperature in ceramic pots and then placed into a box or hole surrounded with an insulating material such as hay, feathers, or moss. The retained heat would continue cooking the food for several more hours, while reducing the resources needed to cook.

The Wonderbag uses the same principle, but is insulated with foam chips, repurposed from furniture factories, which allow it to retain warmth for hours without a heat source. Food is briefly parcooked (meat must be browned) and brought to temperature in a pot over heat; it is then placed in the Wonderbag to cook over the course of several hours. Because the Wonderbag cooks with heat retention, food must be put into the cooker at a higher temperature, so the cooking process continues as the temperature slowly falls. Like its traditional predecessors, the Wonderbag frees users from active cooking and reduces the amount of overall fuel required, making it an environmentally friendly tool.

The implications of powerless cooking are even greater for families living in parts of Africa where cooking is still primarily done over open flames. Women, who often do the cooking, must spend tremendous amounts of time monitoring open fires, and families must have enough firewood to maintain the blaze over long periods of time. Then there are the hazards: burns and smoke inhalation are incredibly common. Indeed, the statistics are staggering—an estimated four million people will die from smoke inhalation from these fires, and over half of those deaths will be children under the age of five.

The Wonderbag alleviates several constraints put on families and their environments. Freed from continually monitoring their food as it cooks, women are able to pursue other activities, spend more time with their children, and acquire new skills, while children spend less time gathering firewood, allowing them more time to attend school. Fewer trees need to be harvested for fuel, reducing carbon emissions and cutting water usage by half. And, without constant open fires, the number of cooking-related accidents drops.

It’s probably the only slow cooker in the world that can make duck confit and change lives.

Wonderbag Sous Vide

Preparing food sous vide is one of the hallmarks of Modernist cooking and is often associated with expensive equipment and intricate applications. Like heat-retention cooking, the idea of cooking food in packages is not new. Throughout culinary history, food has been wrapped in leaves, potted in fats, packed in salts, or sealed inside animal bladders before being cooked. The defining features of sous vide cooking is not packaging or vacuum sealing but rather the ultrafine temperature control that modern technology enables. Using sous vide, you can heat foods to precisely the temperature you want for precisely the amount of time you desire. There is no need to overcook or undercook parts of food to achieve the desired doneness at the center.

It’s a misconception that cooking sous vide has to be an expensive endeavor. Technology has become far more affordable within the past year alone. We’ve demonstrated how to employ the technique using nothing more than a digital thermometer, a pot, some zip-top bags, and a cooler or kitchen sink. Cooking sous vide is a far more approachable, utilitarian technique than most people give it credit for.

We couldn’t help but draw parallels between the thermal-retention of the Wonderbag and cooking sous vide. According to Wonderbag, cooking is simple. “It works in four easy steps: boil it, bag it, stand it, and serve it.” The Wonderbag is essentially a slow cooker—chicken on the bone takes at least two hours to cook; white meat takes at least an hour. Because it does not use direct heat, food will not burn or overcook. You can see why the description sounded remarkably familiar to us.

Because of the similarities to sous vide, we were intrigued by the idea of using the Wonderbag as a portable, affordable water bath. Although it wouldn’t give us precise control over temperature, we were curious to see if we could recreate certain sous vide recipes with the Wonderbag.

Testing

To determine if the Wonderbag could be used to cook food sous vide, we first needed to do some experiments to see how long the Wonderbag could keep our water within the required temperature range.

For the experiment, we outfitted our bag with a thermocouple to log data. As a control, he also logged data from a pressure cooker with the lid locked so water vapor couldn’t escape. Both the pressure cooker and the normal lidded pot he used in the Wonderbag contained 5.76 liters / 1½ gallons of water at a starting temperature of 97 °C / 207 °F.

The Wonderbag performed better than the control. According to the data, the bag retained a target temperature for 4–6 hours. After 10 hours, the water temperature fell to 65 °C / 149 °F. After 16 hours, the water temperature was still above 55 °C / 131 °F.

With these data, we were able to identify recipes that would work with the Wonderbag, but we determined that we would need to adjust our favorite temperatures and times to account for heat loss.

Duck Confit

To demonstrate its versatility, we used the Wonderbag to make duck confit, an adaptation of our Modernist Cuisine at Home Turkey Confit recipe. We recommend cooking duck legs to a core temperature of 60 °C / 140 °F. To account for heat loss incurred while food rests in the Wonderbag, we adjusted our recipe as follows.

We cured the duck in a 1:1 salt and sugar solution overnight to maximize tenderness and minimize the amount of seasoning needed once the duck was removed from the Wonderbag. The duck was put in a Le Creuset Dutch oven with enough duck fat to coat it, and the fat was heated to 97 °C / 207 °F. Once the fat reached our target temperature, the Dutch oven was placed inside the bag with a trivet underneath it to protect the fabric. Thermocouples were positioned in both the duck and the fat. When the duck reached the target core temperature of 60 °C / 140 °F, it was removed from the Wonderbag and allowed to cool completely.

Using the Wonderbag, our duck confit took between 5 and 6 hours to cook; this time will depend on the ratio of fat to duck and how often you check the temperature. Opening the bag allows heat to escape, so only check the temperature when you are close to service time. Food will not overcook or burn; the longer it cooks, the more tender it will become.

To finish, we recommend frying the duck legs in the rendered duck fat. We slowly heated the cooled duck and the fat until it began to sizzle and the skin became crispy. And, because we cured the duck overnight, there was no need to use additional seasoning. The results were incredibly delicious—tender and juicy legs nicely contrasted the crisp bits of rendered fat.

The Wonderbag works best with recipes that take under 6 hours to cook. You won’t be making 72-hour short ribs in this cooker, but tender proteins, such as steak, pork, lamb, and most poultry, will work well.

The versatility of the Wonderbag is exciting, but more so is the impact of this innovative tool. For every bag sold, one is donated to a family in Africa. The Wonderbag is more than just a tool— it’s an extraordinary example of how re-thinking food can change our world. We hope you will visit the Wonderbag site for more information about their foundation and for slow-cooking recommendations.