Step 1

Preheat the oven to 375F. Line a 12-cup muffin pan with paper liners.

Step 2

In a large bowl, whisk together the flour, oats, sugar, baking powder, baking soda, cinnamon, and salt.

Step 3

In a medium bowl, whisk together the milk, oil, eggs, and vanilla until well combined. Stir in the mashed banana. Pour the milk mixture into the oat mixture and stir together until well combined. Stir in the chocolate chips, if using. Divide the batter among the paper liners. (They will be very full.) Sprinkle with extra oats and cinnamon, if desired.

Step 4

Bake for 18 to 22 minutes or until golden brown and the centers feel firm. Let the muffins cool in the pan for a few minutes, then remove and continue cooling on a wire rack.