In a large bowl, beat butter and peanut butter until light and fluffy. Slowly beat in 1/2 of the confectioner's sugar. Mix in 1/4 cup of the cream. Beat in the remaining confectioners' sugar. If necessary, add a little more cream or milk until the frosting reaches a good spreading consistency. Makes enough to frost one 2 layer 9 inch cake or one 9x13 inch cake.