Preheat oven to 425 degrees F. Prepare a 12 cup muffin pan with paper muffin liners.
In a separate bowl, mix white whole wheat flour, dark cocoa powder, baking powder, baking soda and salt. Combine wet and dry ingredients, add in milk and stir until just combined, do not overmix.
Scoop into a muffin pan that has been lightly sprayed with cooking spray. Bake for 15-20 minutes or until tops spring back when touched. Remove from oven and allow to cool. Store loosely covered or in refrigerator.
Combine mashed bananas, softened butter, sour cream and sugar, mix until well combined. Add in eggs and vanilla and mix until well combined.
Add flour, cocoa powder, baking powder, baking soda, salt and chocolate chips. Mix until the ingredients are all combined, but do not over mix.
Let batter sit for 15 minutes, then divided batter equally in prepared muffin pan. If desired, sprinkle additional chocolate chips on top of muffins.
Bake for 5 minutes then REDUCE the temperature to 350 degrees.*
Bake for an additional an additional 13-18 minutes, or until a toothpick inserted into the center of the muffins comes out clean.
Remove pan from oven and transfer to a wire cooling rack. Allow muffins to cool for at least 10 minutes prior to removing from muffin pan.