Chocolate Buttercream: add 3 ounces bittersweet chocolate that has been melted and cooled.
Instructions
Place the butter in the bowl of a stand mixer with the wire whip attachment or in a large bowl with a hand mixer and beat until it is light and fluffy, scraping down the sides of the bowl regularly. This should take at least 5 minutes. Beat in the vanilla extract.
Sift the confectioners sugar to ensure there are no lumps at all. Add the sugar, one cup at a time, to the whipped butter, beating well between additions.
Add the cream slowly until the right consistency is reached. For chocolate buttercream, beat in the melted chocolate.
Store in the refrigerator, but make sure the frosting comes to room temperature before trying to ice a cake. Room temperature frosting will spread more easily. Also, give the frosting a stir before trying to ice your cake. That will also make it fluffier and easier to spread.
Recipe by Blue Jean Chef - Meredith Laurence at http://www.meredithlaurence.com/recipes/buttercream-frosting/