Preheat the oven and prepare your pan: Preheat your oven to 375°F (190°C). Line a 12-cup muffin tin with paper liners or grease it lightly with cooking spray.
Mix the dry ingredients: In a medium-sized bowl, whisk together the flour, cocoa powder, baking powder, baking soda, and salt. Set this mixture aside.
Mash the bananas: In another bowl, mash the ripe bananas until smooth. The riper the bananas, the better the flavor!
Combine the wet ingredients: Add the granulated sugar, brown sugar, beaten egg, melted butter, vanilla extract, and milk to the mashed bananas. Mix well until all the ingredients are combined.
Incorporate the dry ingredients: Gradually fold the dry ingredients into the wet mixture using a spatula. Stir until just combined. Be careful not to overmix, as this can result in dense muffins.
Add the chocolate chips: Gently fold in the chocolate chips, ensuring that they are evenly distributed throughout the batter.
Fill the muffin tin: Spoon the batter into the muffin tin, filling each cup about 3/4 full. You should have enough batter for exactly 12 muffins.
Bake: Place the muffin tin in the preheated oven and bake for 18-20 minutes, or until a toothpick inserted into the center of a muffin comes out clean or with a few crumbs attached. Be sure not to overbake, as the muffins should stay soft and moist.
Cool and serve: Allow the muffins to cool in the pan for 5 minutes before transferring them to a wire rack to cool completely. Serve warm for an extra indulgent treat, or enjoy them at room temperature.