Preheat oven to 350° F. Line a muffin tin with 12 muffin liners.
Mix flour, sugar, baking powder and salt in a large bowl.
Mix mashed bananas, egg, vanilla, melted butter, and milk in a medium bowl.
Stir banana mixture into dry ingredients until just blended. Stir in the chocolate chips. Distribute the muffin mixture evenly into the 12 muffin liners.
Bake for about 25 to 28 minutes or until toothpick inserted in center comes out clean. Carefully remove from oven and let cool at least 10 minutes or more before serving. Enjoy!