Preheat oven to 350°F. Grease a mini muffin pan with nonstick spray.
In a medium bowl, mash avocado with a fork or a potato masher until creamy.
Add peanut butter, melted butter, egg, granulated sugar, brown sugar, and vanilla. Stir to combine.
Add cocoa powder and chocolate chips. Stir until combined.
Pour batter into each muffin cup, approximately 2/3 full.
Bake 18-20 minutes. Cool completely. Sprinkle with powdered sugar before serving.