Egg is sold in a range of standard sizes, the most common being jumbo, extra large, large, and medium. Large eggs are used in most recipes. Chicken eggs are most commonly used; in some areas, duck, goose, and quail eggs are also available. Shell color-brown or white-is purely superficial; there is no difference in quality. Refrigerate in the carton for up to 5 weeks.
To separate an egg:
Crack the egg and hold the shell halves over a bowl. Transfer the yolk back and forth between the halves, letting the white drop into the bowl. Do not cut the yolk (whites containing any yolk will not beat properly). Transfer the yolk to another bowl.
To whisk egg whites:
Using a wire balloon whisk or electric beater on medium speed, beat the whites with broad, sweeping strokes to incorporate air, until the whites form soft peaks or stiff peaks when the whisk or beater is lifted from the bowl.
To fold in beaten egg whites:
Gently stir in one-fourth of the whites. Add the remaining whites. With a rubber spatula, in one stroke, cut through the mixture and scrape across the bottom of the bowl and up the side. Give the bowl a quarter turn and repeat. Continue until the mixture is blended.
To beat egg yolks:
Using a wire balloon whisk or electric beater on medium speed, beat until thickened and a pale creamy color-known as the ribbon stage, when yolks fall from the whisk or beaters in a thick stream that folds on itself and then dissolves.
To hard-cook eggs:
Place the eggs in a saucepan with cold water to cover generously. Bring to a boil. Remove from the heat. Leave in the covered pan for 15-17 minutes. Set the eggs under cold running water until cool. Roll on the counter to crackle the shell, then peel.