In a large bowl, combine the first six ingredients (flour through baking powder). Mix together with a whisk so all dry ingredients are evenly distributed. In a small bowl, combine bananas, oil and egg; stir into dry ingredients just until moistened. Fold in chocolate chips. Fill greased or paper-lined muffin cups three-fourths full. Bake at 350° for 20-25 minutes or until muffins are done.