Preheat the oven to 350 degrees.
Mix brownie batter according to package directions.
Spray mini muffin pan with cooking spray.
Spoon small amount of brownie batter into muffin pan, enough to fill 1/3 to 1/2 full.
Spoon small amount of frosting onto each cup of brownie batter.
Top with more brownie batter, filling cups all the way.
Bake for 15 minutes.
Makes about 36 brownie bites.