Beat egg slightly. Add milk, yogurt, apple sauce, and vanilla. Stir in bananas. Combine remaining ingredients and then add to wet mixture. Stir until just combined. Grease or line muffin tins, pour in batter, then bake at 400F for 16-18 minutes. Immediately remove to cooling rack.
Makes 16 muffins, at 122 calories each. Without the chocolate chips, it's only 102 calories each.