If using a boxed mix (Go with Ghirardelli’s – trust me), prepare brownies according to directions, and bake for 20-25 minutes in a 9 x 13 baking dish.
Remove from the oven and top with chopped peanuts and peanut butter cups. Return them to the oven and bake for 4-6 minutes more.
While the brownies are finishing baking, melt the butter, chocolate chips, peanut butter in a pan over medium heat. Stir in the cereal. Remove brownies from the oven and evenly pour chocolate mixture over the top.