Preheat your oven to 350°F (175°C) and line a muffin tin with paper liners.
In a mixing bowl, mash the ripe bananas with a fork until smooth.
Add the melted butter to the mashed bananas and mix well.
Stir in the baking soda and salt.
Add the sugar, beaten egg, and vanilla extract, mixing until well combined.
Gradually add the flour, stirring until just incorporated; do not overmix.
If desired, fold in chocolate chips or nuts.
Divide the batter evenly among the muffin liners.
Bake in the preheated oven for 18-20 minutes, or until a toothpick comes out clean.
Allow to cool in the pan for 5 minutes, then transfer to a wire rack to cool completely.