Combine butter, chocolate chips, and cocoa powder in a double boiler over med-low heat and stir until melted. If you don’t have a double boiler, put a glass bowl over a saucepan with water. Stir until melted and remove from heat.
Place muffin cup liners in muffin pan and fill 3/4 full. Bake for 18-20 minutes or until fork inserted comes out clean. Remove from pan and allow to cool fully.