This is great with Aunt Helen's Chocolate Cake. The recipe calls for a cup of chocolate chips but I always throw the whole bag in! The recipe calls for chocolate chips but the peanut butter chips on that chocolate cake is divine!!! I have also used chocolate chips and white chocolate chips too, up to you. But if you like peanut butter frosting do the peanut butter chips, you won't be sorry. Remember to work fast, this frosting "sets up to fudge" very quickly.
In a small saucepan combine the butter, milk and sugar. Let it cook to a full rolling boil. Once you have it boiling be sure to stir it constantly and cook for a full minute and a half. After it has cooked at a full rolling boil for a minute and a half remove from heat.
Quickly add in the vanilla and the chips. Stir briskly until smooth (work fast this starts setting up fast)
Pour over your cooled cake while this frosting is still warm. Do not let the frosting stand or cool before putting it on the cake. This frosting will begin to set up very quickly.