It can be a challenge to make perfect hard cooked eggs, (incorrectly called hard boiled). Here is a full-proof method. Place eggs in a saucepan in a single layer. Add cold water to cover the eggs by 1 inch. Heat the eggs over high heat just to boiling. Remove the pan from the hot burner and let eggs stand in the hot water: 9 minutes for medium-size egg; 12 minutes for large eggs; and 15 minutes for extra large. Rinse in very cold water and store in the refrigerator in their shells for up to one week. Hard cooked eggs are perishable and should not be kept at room temperature for more than 2 hours.
This method produces tender hard cooked eggs without cracked shells. Boiling or over-cooking produces rubbery whites and the dreaded green tinge or ring around the yolk. The ring is caused by sulfur and iron compounds that occur naturally in the egg. It can also be caused by a high iron content in cooking water. In either case it does not affect taste and the egg is safe to eat.
