Mousseline is a type of fluffy, usually pureed, mixture that has a consistency similar to mousse. It is often made with meats, particularly chicken or fish, but may also be made without. Mousseline almost always uses some sort of cream. The term may also refer to a Hollandaise type sauce that also uses whipping cream.
Recipes of this food are highly variable. The only necessary ingredients are cream and eggs whites. Sugar is also normally added in the sweet versions. Mousseline is named, however, for the mousse-like texture created by certain ingredients and the cooking process, not the ingredients themselves.
When making meat mousseline, seafood or chicken can be used. Fish, such as salmon, is a popular choice. Shrimp, or a combination of fish and shrimp is also an option. Shallots, salt, and white pepper are often added to meat mousseline as seasonings. Egg whites and butter are also usually included.
To make, all the ingredients except the cream are pureed in a food processor. Once the mixture is smooth, the cream is added slowly while the processor runs. Alternately, the mixture may be chilled, and then half the cream is folded into the chilled dish. The other half is whisked or beaten until it is stiff, and then it is folded into the mix as well.
The fluffy result can be placed over vegetables or layered in dishes. The mousseline may also be cooked in buttered ramekins. The ramekins are then placed in a broiler pan filled with water, covered with parchment paper, and allowed to bake. Sauce, such as tomato cream, is often included with mousseline prepared in this way.
Mousseline can also be used as cake filling. Thoroughly combining pastry cream and cold sliced butter in a mixing bowl creates a simple, sweet filling base to which fruit, chocolate, or another flavoring can be added. The mixing should be done with a paddle attachment initially, then with a whisk about half way through.
Cake frosting is another use for mousseline. A simple buttercream frosting can be made with butter, cream of tartar, egg whites, and sugar. Similar to making meringues or angel food cake, the egg whites are beaten until foamy, then the cream of tartar is added and the whites are beaten again.
Once the mixture begins to stiffen, sugar is gradually added and the whites are beaten until stiff. Cooks check the stiffness of mixtures by removing the beater blades. If firm peaks are left behind, the mixture is ready.
Sugar water, heated until it becomes syrupy, may be added once the whites are stiff. Afterward, butter is beaten into the mix. Once complete, a flavoring may be included. Fruit or chocolate syrups, nut extracts, or even espresso powder can be added to flavor the mousseline frosting.