Although the term "hard-boiled" is more commonly known, "hard-cooked" is more accurate because the eggs should not be cooked at a boil.
1. Place 4 large eggs in a saucepan, and add enough water to cover them by 1 inch. Bring water to a simmer over high heat. Remove from heat, cover, and let stand 12 minutes.
2. Drain and rinse under cold running water. Unpeeled eggs can be kept in the refrigerator for up to 1 week.
If you cut open an undercooked egg, the yolk will still be damp and will be a dark-gold color instead of pale yellow.
The white of a hard-cooked egg should be tender, the yolk fluffy but firm.
The white of an overcooked egg is rubbery; the yolk develops an unattractive (though harmless) greenish-gray coating.