A successful soufflé, puffy and golden brown, is a triumph of the cook’s art, rising high above the rim of its dish in apparent disregard of gravity. A soufflé is made by mixing a highly flavored sauce or purée with stiffly whipped egg whites, which expand in a hot oven to give the mixture its dramatic height. Three points are crucial: a soufflé base of the right consistency, egg whites that are stiffly beaten, and careful folding of the two together so as to retain maximum volume and lightness. To ensure lightness, one-to two-thirds more egg whites than yolks are added to most soufflés; the volume of beaten whites should be at least double that of the basic mixture. The volume will decrease when the whites are folded into the basic mixture, but rise again when the soufflé puffs up in the oven. In the oven, a soufflé should increase by at least half, to as much as double its original volume.