Preheat oven to 350 degrees. Spray or grease 36 mini muffin cups or 18 regular size.
Combine the flour, cocoa, baking powder, and salt. Combine the butter, eggs, vanilla, and sugar. Mix the flour combination with the butter combination.
Spoon batter evenly into muffin cups (about 1 heaping teaspoon). (If you are using the larger muffin tins use 2.) Bake for 13-15 minutes or until top is set and a toothpick inserted into center comes out slightly wet. Adjust time for larger ones.
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 chocolate chips and peanut butter chips. Cool completely in pan