In French, the word mousse simply means froth or foam and includes any dish, sweet or savory, that is light and airy, with a flavored base that has usually been puréed and then folded into beaten egg whites or whipped cream. Sweet mousses are made from several different bases, including fruit purée, pâte à bombe, coffee, liqueur, or chocolate. Savory mousses can be made with meat, fish, shellfish, or vegetable purées.
The characteristic mousse texture is achieved by folding stiffly beaten egg whites or softly beaten heavy cream into a puréed base. The cream should not be too stiffly beaten or it will begin to have a strong, buttery taste and will produce a heavier mousse, which is not desirable. When folding the beaten egg whites or cream into the base, one quarter of the beaten ingredients is first added to lighten the base and then the remaining three quarters are folded in all at once. The air bubbles from the beaten egg whites or cream are trapped in the dessert base and provide the airy, almost spongelike texture.