Step 1

Preheat oven to 350 degrees. Place muffin liners into a muffin tin.

Step 2

Add the butter and sugars to a mixing bowl and beat until well combined.

Step 3

Beat in the egg, vanilla, banana, and sour cream until just combined.

Step 4

Stir in the flour, cocoa powder, baking soda, and salt.

Step 5

Scoop the batter into the muffin wells, filling them 2/3 of the way full.

Step 6

Sprinkle the top with chocolate chips and gently press them into the batter.

Step 7

Bake for 18-20 minutes or until a tester comes out clean.

Step 8

Let the muffins cool before serving.