Preheat oven to 350 degrees. Spray or grease 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. If not then tap the centers with the back of a teaspoon to make a hole for the peanut butter.
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. Top with semi-sweet chocolate chips and peanut butter chips. Cool completely in pan.