This recipe is a little much to be the only frosting on a cupcake or a cake. It is better as a filling with regular buttercream as the icing. I got it from www.allrecipes.com.
1/2 Cup Butter
1 Cup Creamy Peanut Butter
4 Cups Powdered Sugar
1/3 Cup Heavy Cream
It is very stiff like this. I add more heavy cream while the mixer is going until I get the consistency I need.
I hope you enjoy. I made dark chocolate cupcakes with this and everyone loved them.