1.Preheat oven to 180°C (160°C fan-forced). Line two 12-hole mini muffin pans (1-tablespoon/20ml) with paper cases.
2.Combine flour, brown sugar and rolled oats in a medium bowl. Combine egg, milk, apple juice and vegetable oil; stir into the flour mixture.
3.Add half a finely chopped medium ripe banana (100g) and 50g (1½ ounces) finely grated dark chocolate; stir gently to just combine. Divide mixture into pan holes. Bake for 15 minutes or until a skewer inserted into the middle comes out clean.
4.Stand muffins in pans for 5 minutes before turning, top-side up, onto wire racks; sprinkle warm cakes with an extra 50g (1½ ounces) finely grated dark chocolate. Cool muffins.