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.
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.