Preheat the Oven:
Preheat your oven to 350°F (175°C). Line a muffin tin with muffin liners or grease it lightly.
Prepare the Dry Ingredients:
In a mixing bowl, whisk together the flour, cocoa powder, baking soda, and salt until combined.
Prepare the Wet Ingredients:
In another bowl, mash the ripe bananas until smooth. Add the granulated sugar, brown sugar, eggs, melted butter, milk, and vanilla extract. Whisk until smooth and fully combined.
Combine the Wet and Dry Ingredients:
Gradually add the wet mixture to the dry ingredients, stirring gently until just combined. Be careful not to overmix.
Add Chocolate Chips:
Fold in the mini chocolate chips and chocolate chunks (if using) until evenly distributed.
Fill the Muffin Tin:
Divide the muffin batter evenly among the 12 muffin cups, filling each about ¾ full.
Bake:
Bake for 18–20 minutes, or until a toothpick inserted into the center of a muffin comes out clean with a few crumbs.
Cool and Serve:
Let the muffins cool in the pan for 5 minutes, then transfer to a wire rack to cool completely. Serve and enjoy!