Preheat oven to 350 degrees and line 12 muffin cups with liners.
In a large bowl, mix flour, both sugars, baking powder, and salt.
In a medium bowl, mix mashed bananas, egg, melted butter, milk, and vanilla extract.
Stir wet ingredients into dry just until there are no large streaks of flour.
Stir in chocolate chips.
Fill each muffin cup ¾ full and bake until muffin tops are firm when pressed gently, about 30 minutes.
