Mexican Chocolate Frosting

1/4 cup softened butter or margarine
1/2 cup unsweetened cocoa powder
1/2 cup sour cream
4 cups confectioners' sugar
1 tablespoon coffee liqueur

Blend butter or margarine and cocoa powder. Add remaining ingredients. Beat until very smooth.

This yields enough frosting to fill and frost a 2-layer 9-inch cake.