Preheat the oven to 350°F (175°C). Line a 12-cup muffin tin with paper liners or grease the cups.
In a medium bowl, whisk together the all-purpose flour, baking powder, baking soda, and salt.
In a large bowl, combine the mashed bananas, granulated sugar, egg, melted butter, and vanilla extract. Mix until well combined.
Gradually add the dry ingredients to the banana mixture, stirring gently until just combined. Do not overmix.
Fold in the semisweet chocolate chips evenly into the batter.
Divide the batter evenly among the 12 muffin cups, filling each about 3/4 full.
Bake for 18 to 20 minutes, or until a toothpick inserted into the center of a muffin comes out clean.
Remove the muffins from the oven and let them cool in the tin for 5 minutes, then transfer to a wire rack to cool completely.