In a large pot, melt the butter over medium heat. Add marshmallows and turn heat to low. Stir until completely smooth. Remove from heat and quickly stir in peanut butter. Add cereal.

Fold in the mini marshmallows. Pour Krispies treats into a 9-inch square baking dish lined with parchment paper or buttered foil. DO NOT press them tightly. Gently level the top and spread melted peanut butter morsels over the top.

Once cooled slightly, top the melted peanut butter morsels with the peanut butter cups. Press them in so they stick! Allow to set, about one hour. Cut into squares and store in an airtight container.