Buttercream

Buttercream (also known as butter cream, butter icing, and mock cream) is a type of icing or filling used inside cakes, as a coating, and as decoration. In its simplest form, it is made by creaming butter with powdered sugar, although other fats can be used, such as margarine or lard. Colorings and flavorings are often added, such as chocolate, fruit purees, and various extracts. Buttercream is a common topping for cupcakes, sponge cakes, butter cakes, and other desserts.

Whether buttercream with no butter or a butter equivalent can rightly be called buttercream is debated among bakers, pastry chefs, and cake decorators.

https://en.wikipedia.org/wiki/Buttercream