Preheat the oven to 180C.
Whisk together the flour, the oats (minus the extra for topping), baking powder, bicarbonate of soda, salt, and cinnamon in a small bowl and set aside.
In a large bowl, add the brown sugar and melted butter/oil and whisk vigorously for 1 minute.
Add the eggs, mashed bananas, milk, and vanilla and whisk until fully combined.
Add the dry ingredients to the wet ½ cup at a time, beating continuously until smooth, then stir in the chocolate chips/blueberries.
Line the muffin tin with parchment baking cups and fill ¾ of the way, then top with the remaining 2 tablespoons of oats.
Bake for 25 minutes until a toothpick comes out clean.
Let cool for 5 minutes and then move to a wire rack.
