Preheat oven to 350°F (175°C) and grease a 9x5 inch loaf pan.
In a large mixing bowl, mash the ripe bananas with a fork until smooth.
Stir the melted butter into the mashed bananas.
Mix in the baking soda and salt.
Stir in the granulated sugar, beaten egg, and vanilla extract.
Mix in the flour until just incorporated; do not overmix.
Fold in the semi-sweet chocolate chips.
Pour the batter into the prepared loaf pan.
Bake for 55 to 60 minutes, or until a wooden skewer inserted into the center comes out clean.
Cool in the pan for 10 minutes, then transfer to a wire rack to cool completely.