Preheat your oven to 350°F (175°C).
Prepare your muffin tin by lining it with paper liners or greasing it with butter or cooking spray.
In a separate bowl, mix the dry ingredients: flour, baking soda, and salt.
Mash the ripe bananas in a mixing bowl until smooth.
Combine the wet ingredients: mashed bananas, melted butter, sugar, beaten egg, and vanilla extract.
Gradually add the dry ingredients to the wet mixture and stir gently until just combined.
Fold in the semi-sweet chocolate chips.
Divide the batter evenly among the muffin cups, filling each about 2/3 full. Bake for 18-20 minutes.