An easy recipe for peanut butter frosting on BettyCrocker.com calls for the cook to combine 1 cup of pre-made vanilla frosting with 1/3 cup of peanut butter and 2 to 3 teaspoons of milk. Easy peanut butter frosting recipes are also available on BonAppetit.com and Epicurious.com.
To prepare peanut butter frosting according to the Bon Appetit recipe, sift 1 1/2 cups of powdered sugar before using an electric mixer to thoroughly blend the sifted sugar with 8 ounces of softened cream cheese, 1 stick of softened unsalted butter and 1/2 cup of smooth peanut butter in a bowl. The mixture is ready to use when it is creamy and spreadable.
Follow the Epicurious recipe for peanut butter frosting by using an electric mixer to combine 1 cup of powdered sugar, 3/4 cup of creamy peanut butter, 1/2 stick of softened unsalted butter and 1/4 teaspoon of vanilla extract in a bowl. When the mixture is well-combined, assess the texture of the frosting. If the frosting is too thick, gradually beat in very small amounts of whipping cream, one teaspoon at a time, until it reaches an ideal consistency.
Bon Appetit and Epicurious caution that old-fashioned peanut butter and freshly ground peanut butter are not suitable for use in these particular recipes.