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.
Mix till desired consistency, about 5 minutes.
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.
Notes
Pro Tip: Start with less liquid and add more as needed, you can always add more milk or cream, but you can't take it away! The frosting should hold its shape but still be easy to spread.