AllRecipes.com and the official websites of Wilton and Betty Crocker offer recipes for peanut butter icing. The recipes use ingredients such as shortening, vanilla extract, milk and peanut butter. The icing goes well on chocolate cake.
A recipe on AllRecipes.com makes a creamy no-cook peanut butter icing in 10 minutes. To make it, beat 1 cup of butter in a bowl with an electric mixer until fluffy. Add 1/2 cup of creamy peanut butter, 1 teaspoon of vanilla extract and a pinch of salt, and beat until everything is well incorporated. Slowly pour 4 cups of confectioner's sugar into the mixture while continuing to beat. Add 1/4 cup of milk or enough to make the icing a desired thickness.
Wilton's recipe makes a peanut butter buttercream icing for chocolate cupcakes. Cream 1/3 cup of solid vegetable shortening and 1/3 cup of butter with an electric mixer. Add 3/4 cup of peanut butter and 1 teaspoon of vanilla extract. Gradually add 4 cups of confectioner's sugar 1 cup at a time, beating on medium speed. When the icing appears dry, add 4 to 6 tablespoons of milk 1 tablespoon at a time, and beat until the icing is fluffy.
Betty Crocker's recipe makes a peanut butter icing for a chocolate sheet cake. It involves heating the ingredients in a saucepan and placing salted peanuts over the finished icing.