01 - Preheat oven to 350°F. Line a 12-cup muffin tin with paper liners or grease lightly.
02 - In a large bowl, whisk together flour, sugar, baking soda, baking powder, and salt.
03 - In another bowl, combine mashed bananas, melted butter, milk, eggs, and vanilla extract. Mix until smooth.
04 - Gently fold the wet ingredients into the dry ingredients until just combined, avoiding overmixing.
05 - Fold in the semi-sweet chocolate chips evenly.
06 - Divide batter evenly among the muffin cups, filling each about three-quarters 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 tin for 5 minutes, then transfer to a wire rack to cool completely.