Cold Mousses and Soufflés: Reinforcement from Fat and Gelatin In addition to being served as is in the form of a sugar-and heat-stabilized meringue, an egg foam can also be enrobed in a mixture of other ingredients, for which the foam serves as a hidden scaffolding. The cold mousse and cold soufflé (essentially a mousse molded to look like a hot soufflé that has risen above its dish) hold well for hours, even days, and require only minimal cooking. Instead of being stabilized when heat coagulates egg proteins, these mixtures are stabilized when cold congeals fats and gelatin protein.