Preheat oven to 350 degrees. Grease or line a 9×13 inch baking dish or cookie sheet with parchment paper. Cream butter and sugar together in a large mixing bowl. Add peanut butter and continue mixing. Add eggs one at a time, mixing well after each egg. Add in vanilla. Combine flour, oats, baking powder, and salt in a small mixing bowl. Add the flour mixture slowly stirring until well combined. Spread dough on the sheet pan and pat firm.Bake for about 30 minutes. Meanwhile, make peanut butter topping. In a bowl, blend peanut butter, powdered sugar and milk. When cookie is done, remove from oven and immediately sprinkle top with chocolate chips. Spoon peanut butter and powdered sugar mixture over chocolate chips and swirl with a knife or spoon. Dot with Reese’s chopped peanut butter cups. Refrigerate for several hours to harden. Cut into squares and enjoy!