Line 16 muffin moulds with waxed paper muffin cases. Preheat oven to 200°C.
To prepare batter:
Make a well in the flour mixture. Pour in the whisked wet ingredients and mix to a creamy batter. Stir in banana and chocolate.
Pour batter into prepared muffin cases. Bake for 10 minutes, reduce oven temperature to 180°C and bake for another 15 minutes. Cool muffins in pan for 5 mins before turning out onto a wire rack to cool.