Preheat oven to 350°F. Spray a 24 mini muffin pan with non-stick cooking spray. Set aside.
In a medium bowl, add brownie mix and all of the remaining ingredients except for garnish. Stir by hand with a wooden spoon until combined, about 50 strokes. Do not overbeat.
Pour about 1 tablespoon of batter in each muffin cup. You should be able to fill all 24 cups. Bake for 20 minutes. Let cool. Garnish, if desired. Only garnish the muffins you are going to eat right away. Serve immediately or store plain muffins in an airtight container for a few days at room temperature or up to a week in the refrigerator. They can be frozen for 1 month.