Start by separating cold, fresh eggs by breaking the egg shell in half, and over a bowl, passing the yolk from shell to shell, allowing the egg white to drip into the bowl while the yolk remains in the shell. Cover the yolks with cold water to keep from hardening, and reserve for another use.
Let the whites sit at room temperature for half an hour.
Add 1/4 teaspoon or so of cream of tartar to help stabilize the egg whites.
When the egg whites are at room temperature, beat with a whisk or an electric mixer set to a high speed.
Beat the whites until they are uniformly stiff. Now you are ready to fold.
Take a small amount of the beaten egg whites and whisk these into the mixture to lighten the base.
Next, place a third of the egg whites on top of the batter. Using a rubber spatula, gently push down through the whites and batter and, scraping the bottom of the bowl, lift some of the batter up and over the whites.
As you fold the whites into the batter, turn the bowl about a quarter-turn. Continue folding the batter and turning the bowl until the egg whites are about halfway incorporated, and the batter is lighter. Add another third of the egg white mixture, folding and turning, and then the final third. Fold until you have no traces of egg white left.