Alrighty.. I know this is not a "real" recipe but it's so easy and quick and my sister loves peanut butter.
I just used a regular box of Family -Sized Brownie mix and followed directions on box.
Mix and pour half of batter into your prepared pan. Sprinkle a layer of chopped up Peanut Butter Cups on batter, now cover with the rest of your brownie batter. Place about 6 tbsp of peanut butter on top layer (I melted mine a little to make it easier to spread). With knife marble the peanut butter through brownie batter. Everyone will love these, I promise!