Preheat oven to 350°F. Lightly coat regular-sized muffin tin with cooking spray (or line with papers).
In a large bowl, mash bananas with fork. Whisk in egg, milk, and sugars.
In a separate bowl, whisk together flour, baking soda and salt. Slowly add to wet mixture and mix until combined. Stir in chocolate chips.
Spoon equal amounts of batter into 12 muffin cups. Bake 25 to 30 minutes, or until toothpick inserted in center comes out clean. Cool 10 minutes in pan, then remove to a wire rack to cool completely.
Why is it important to use the miniature chocolate chips? They spread out more... giving more chocolate flavor to more parts of the muffin. I always find that using regular-sized chocolate chips in a muffin is just a little too much.