Time and Temperature
An egg is a small chemistry laboratory sealed inside a shell. The white is mostly water and protein. The yolk contains water, protein and fat. As the egg heats, its proteins unfold and link together, turning liquid into solid. But the white and yolk don’t cook at the same rate, and the yolk doesn’t suddenly jump from raw to hard. It moves gradually from liquid to creamy to jammy to firm.²
The timing was new to me. Growing up, my mother cooked eggs the same way she cooked a turkey: put them in the water when the meat went into the oven and boil them until the meat was done.
Those eggs weren’t soft-boiled, medium-boiled or hard-boiled. They were thoroughly defeated. The yolks had the pale, powdery texture of construction material, usually surrounded by a green-gray ring. I assumed that was simply what a boiled egg looked like.
Kenji’s photograph of eggs cooked at 30-second intervals was a revelation. Thirty seconds could separate a flowing yolk from a jammy one, or a moist hard-cooked egg from the sort I grew up with. “Boil it until it looks done” isn’t a method.
A timer is a method.
How to Boil an Egg
Bring enough water to cover the eggs to a full boil, then lower large refrigerated eggs gently into the water with a spoon or small strainer. Start the timer immediately.
At six minutes, the white is set and the yolk remains liquid, rather like a poached egg that comes with its own wrapper. At seven minutes, the yolk is creamy and soft. At eight, it is mostly cooked, deep yellow and still moist in the center. Ten to twelve minutes gives you a hard-boiled egg, though there is a considerable difference between a tender ten-minute yolk and a twelve-minute one moving toward chalk.³
The exact timing will vary slightly with egg size, starting temperature and the vigor of the boil. The point isn’t that one number is sacred. The point is to find the number you like and repeat it.
Starting in boiling water gives you a clear starting line. In the cold-water method, the eggs are already cooking while the water heats, and that heating time changes with the pan, the stove, the amount of water and the number of eggs. Kenji’s testing also found that a hot start generally produces eggs that peel more reliably.³
When the timer rings, remove the eggs immediately. Put hard-boiled eggs into ice water to stop the cooking. For an egg you want to eat warm, cool it only until you can handle it. Crack the shell all over and peel under cool running water. The water helps separate the shell and membrane, and it keeps you from burning your fingers, which is an underrated culinary technique.
Why Some Eggs Peel Better
Very fresh eggs are often difficult to peel because the white clings tightly to the membrane under the shell. As the egg ages, carbon dioxide escapes through the porous shell, the chemistry of the white changes and the air pocket grows. That is why a slightly older egg may be better for boiling, while a very fresh one is often better for frying or poaching.³
There are endless tricks for easier peeling: vinegar, baking soda, pinholes and specialized gadgets. The most dependable approach is simpler. Use eggs that aren’t extremely fresh, start them in boiling water, cool them promptly and peel them under water.³