Peanut Butter Brownie Cups

In search for something different to make for Hunter's 4th birthday party I came across these on www.pinterest.com.  They were a big hit at Hunter's party and I will definitely be making them again.  They are a perfect size for children.
Makes 40 brownies as adapted

1 box of your favorite brownie mix
1/2 cup peanut butter chips
1/2 cup semi-sweet chocolate chips
3/4 cup creamy peanut butter

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.

Note:  You could do so many variations on this recipe.  For filling variations other than peanut butter you could use, cream cheese mixture, cherry pie filling, reeses peanut butter cups, chocolate kisses, etc.