Crème Mousseline

In its most basic form, this is a buttercream created by whipping an equal amount of softened, unsalted butter into crème pâtissière. In some recipes, a lesser amount of butter may be added and gelatin may be used to ensure the necessary stability to the finished icing. Confectioners’ sugar is sometimes added for additional sweetness.

You may also find that some pastry chefs refer to “decorator’s icing” or “decorator’s buttercream.” Sometimes these terms describe the pâte à bombe–based buttercream, but as often as not, it refers to an icing made from vegetable shortening and confectioners’ sugar that is used to make extremely stable cake decorations such as flowers and leaves, for mass-produced cakes or for cakes that might have to stand for a long period of time at room temperature. It may also be called “rose paste.”