
Mix flour, baking powder, baking soda and sugar together.
In another bowl, mix egg, milk and melted butter together. Pour it into dry ingredients, mix well.
Use a fork to mash the banana, add in banana and chocolate chips.
Put the batter into muffin tin (till the top), pop in preheated oven at 210C, bake for 8 minutes. Then lower the temperature to 180C for extra 8 - 10 minutes.