Preheat your oven to 350°F and line a muffin tin with paper liners.
Mash the bananas in a large mixing bowl until smooth.
Stir in the melted butter, sugar, egg, and vanilla.
Sprinkle the baking soda and salt over the mixture and stir.
Add the flour and gently fold until combined. Don’t overmix.
Fold in the chocolate chips.
Scoop the batter into muffin cups, filling each about 2/3 full.
Bake for 20 minutes or until a toothpick inserted in the center comes out clean.
Cool for 5 minutes in the pan, then transfer to a wire rack.