Buttercream frosting is rich, sweet and well-suited for decorating cakes and pastries. Decorator's frosting must be able to keep its shape as it dries slightly to prevent heat or humidity from ruining it. Buttercream for decorators must be very stiff, and although it can be made by hand, a mixer will make the job easier. Buttercream will naturally be an ivory colour unless clear vanilla is used, and that can be found in most speciality kitchen shops.
Cream the butter and shortening together in the mixer bowl at low speed. Add the vanilla.
Add the sugar slowly into the bowl while the mixer is running, allowing the sugar to thoroughly incorporate into the butter. Scrape the sides as needed. This mixture should be very stiff.
Add cream 1 tbsp at a time to soften the mixture slightly. The mixture should still be stiff. If it gets too thin, add more confectioners' sugar.
Remove frosting from bowl. Cover tightly in storage container and refrigerate. Frosting will keep up to two weeks in the refrigerator.
Add food colouring to small quantities of icing if you want to accent the white frosting with coloured decorations.