A springy, light egg white and bright yellow, creamy yolk is the goal of making a hard-boiled egg. This yolk can be spread on toast, add texture to salads, or even top a steak. However, the most common mistake when cooking eggs is overdoing them, resulting in yolks with green edges, gray tinges and chalky interiors. There are several steps during the cooking process that are integral to creating a perfectly creamy yolk.
Bring any eggs for boiling to room temperature. This allows them to cook evenly and quickly, with the yolk cooking at the same time as the egg. If using eggs straight out of the refrigerator, the whites can be overcooked while the yolk remains undercooked. Use eggs for boiling that are fresh, but not brand new --between 3 to 5 days old -- as they result in a creamier yolk and a better consistency than older eggs, yet are easier to peel for serving.
Plain water is best in the cooking pot, don't add salt, baking powder, or baking soda. Cook the eggs in a small pan with only enough water to cover them by 1/4 inch. This prevents them from moving around too much during the cooking process. Do not bring the pot to a fast, rolling boil, as this can bounce the eggs and cause them to crack. Instead, use a low simmer for cooking the eggs.
A creamy yolk with minimally set egg whites takes about 3 minutes in simmering water. For set egg whites and a yolk that remains creamy, cook for 4 minutes. Be cognizant that the eggs continue to cook after they are removed from the pot, so are best served right away. Use a kitchen timer that has been set just after placing the eggs in to the water for greatest accuracy. If unable to use eggs that are room temperature, set the timer for 1 minute longer than desired when using refrigerated eggs.
Bake the eggs in the oven at 325 degrees Fahrenheit for 30 minutes. This low temperature cooks the eggs slowly, and allows heat to permeate evenly throughout the egg. When cooked, remove the eggs from the oven and place them gently in a bowl filled with cold water for 10 minutes. A good alternative to boiling, the eggs appear similar to their boiled counterparts when served, with a creamy yolk.