01 - Preheat oven to 350°F. Line a 12-cup muffin tin with paper liners or lightly grease the cups.
02 - Whisk together flour, baking powder, baking soda, and salt in a medium bowl until evenly mixed.
03 - In a large bowl, blend mashed bananas, sugar, melted butter, milk, egg, and vanilla extract until smooth.
04 - Add the dry ingredient mixture to the wet ingredients and fold gently until just combined, avoiding overmixing.
05 - Fold semi-sweet chocolate chips into the batter evenly.
06 - Distribute the batter equally among the prepared muffin cups, filling each about three-quarters full.
07 - Bake for 18 to 22 minutes, or until a toothpick inserted into the center comes out clean or with a few moist crumbs.
08 - Allow muffins to cool in the pan for 5 minutes, then transfer to a wire rack to cool completely.