01 - Preheat oven to 350°F and line a 12-cup muffin tin with paper liners or grease lightly.
02 - In a large bowl, whisk together flour, cocoa powder, baking powder, baking soda, and salt until evenly mixed.
03 - In a separate bowl, whisk mashed bananas, sugar, oil or melted butter, eggs, vanilla extract, and milk until smooth and combined.
04 - Pour wet ingredients into dry ingredients and gently stir until just combined, avoiding overmixing.
05 - Carefully fold semisweet chocolate chips into the batter.
06 - Divide batter evenly into muffin cups, filling each about 3/4 full; optionally sprinkle extra chocolate chips on top.
07 - Bake for 18 to 22 minutes or until a toothpick inserted in the center comes out with a few moist crumbs.
08 - Let muffins cool in the tin for 5 minutes before transferring to a wire rack to cool completely.