Preheat oven to 400F degrees. Line muffin tin and set aside.
In a large bowl, combine egg, milk, banana, oil and brown sugar until combined. Set aside.
In a small bowl mix together flour, baking powder, salt, cinnamon and nutmeg. Gradually add dry ingredients to banana mixture until moist (it might still be a little lumpy). Gently mix in chocolate chips. Fill muffin tins 2/3 full and bake for 15-20 minutes or until toothpick comes out clean. Let cool or enjoy while the chocolate is nice and melted :)