Perfection is the goal here
How do you cook a perfect hard-boiled egg? It's really simple. Arrange the eggs in a single layer in a saucepan or deep skillet. Add just enough tap water to cover. Bring to a boil and cook one minute. Remove from the heat and let them stand at least 15 minutes.
Because the water begins to cool as soon as the heat is turned off, the eggs never overcook the way they can if you leave them at a steady simmer. You get eggs with whites that are firm but not rubbery and yolks that are bright orange and moist.
Furthermore, you never wind up with split or cracked eggs. Those problems happen when you add cold eggs to boiling water and are caused by the sudden expansion of the air bubble inside the shell because of the heat. Since eggshells are porous, if you warm the egg slowly that air eases out gently (if you watch closely, you'll see the bubbles).