Folding in Whipped Egg Whites

Whip the whites to soft or firm peaks, depending on the recipe. Stir about a quarter of them into the heavy base, such as melted chocolate or yolk batter, to loosen it. You'll lose some air in that first portion, and that's fine. Add the rest on top. Cut down through the middle with a large spatula, sweep along the bottom and up the side, turning the bowl a quarter turn each time. Stop as soon as no white streaks remain. Stirring knocks out the air you just whipped in.