Bake Chocolate Cake Mix (1 box) according to instructions in muffin form.
Place on a metal cooling rack until cool enough to handle.
For the frosting, cream the Butter (1 cup), Brown Sugar (1 cup), and Creamy Peanut Butter (1 cup) until creamy.
Next, fold in the Powdered Confectioners Sugar (3 cup) in two equal parts. Add in Heavy Cream (7 tablespoon) and mix until creamy and thick.
Fill the pastry bag by placing the pastry bag in a tall glass, folding the top of the bag over the sides. Add the frosting. When you are done filling simply roll up the sides and push the frosting down to the tip.
To frost cupcakes, start at the edge of the cupcake and work your way around the cupcake in a circle to the middle.
Top each cupcake with PayDay Bars (2) crumbles. Serve immediately or refrigerate until ready to eat.