In a large bowl, combine the flour, sugar, baking powder, baking soda and salt. In another bowl, combine the egg, oil, yogurt and vanilla. Stir into dry ingredients just until moistened. Fold in bananas and chocolate chips. Fill greased or paper-lined muffin cups two-thirds full. Bake at 350 degrees F for 22-25 minutes or until a toothpick comes out clean. Cool for 5 minutes before removing from pans to wire racks.
Makes 32 muffins