Preheat the oven to 350°F (175°C) and line a muffin tin with paper liners.
In a bowl, mash the ripe bananas until smooth.
Add the melted butter to the mashed bananas and mix well.
Stir in the baking soda and salt.
Add sugar, beaten egg, and vanilla extract, mixing until combined.
Gradually fold in the flour, being careful not to overmix.
Gently add the chocolate chips to the batter.
Divide the batter evenly among the muffin cups.
Bake for 20-25 minutes, or until a toothpick comes out clean.
Let cool for a few minutes before transferring to a wire rack.