1. Preheat oven to 350 degrees. Line twelve 1/3 cup muffin cups with foil muffin liners.
2. Mix flour, sugar, baking powder, and salt in a large bowl. Mix mashed bananas, egg, oil, and milk in a medium bowl. Stir banana mixture into dry ingredients until blended (don't overmix). Stir in chocolate chips.
3. Divide batter among prepared muffin cups, filling each about 3/4 full. Bake muffins for 32 minutes or until tops are pale/golden and a tester that is inserted into the middle of the muffin comes out clean. Transfer muffins to a cooling rack and let cool.