Preheat oven to 350 degrees. Spray 40 mini muffin cups
Prepare boxed brownie mix as directed. Spoon batter evenly into muffin cups (about 1 heaping teaspoon). Bake for 13-15 minutes or until top is set and a toothpick inserted into center comes out slightly wet. After brownies are out of the oven, wait for centers to fall. This will happen upon cooling. This did not happen for me, so I used my index finger and poked a hole in the center. I went slightly deep so I could put more peanut butter in the middle. I took them out of the muffin tin and placed them on my work surface because I found this way easier to assemble them instead of still in the muffin tin, but its your preferance.
Place peanut butter in a small microwave-safe bowl. Microwave on high for 45 seconds then stir. While brownies are still warm spoon about half a teaspoon of peanut butter into the center of each brownie.(I did not measure this because I did slightly deeper hole, so you made need more peanut butter) Top with chocolate chips* and peanut butter chips*. Cool completely in pan. *I just used 3 each of both chips, they fit perfectly.
You should wait to eat these when the peanut butter is cooled and set. Warning, these are very addicting..please enjoy