01 - Preheat oven to 350°F. Line a 12-cup muffin pan with paper liners or grease lightly.
02 - Whisk together flour, sugar, baking soda, baking powder, and salt in a large bowl.
03 - In a separate bowl, stir mashed bananas, melted butter, milk, eggs, and vanilla extract until smooth.
04 - Gently fold wet ingredients into dry ingredients until just combined, avoiding overmixing.
05 - Fold in the semi-sweet chocolate chips evenly into the batter.
06 - Divide batter evenly among muffin cups, filling each about 3/4 full.
07 - Bake for 18 to 20 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.