Preheat oven to 375 degrees F.
In a medium bowl, combine flour, oats, white sugar, brown sugar, baking powder, baking soda and salt. Stir until ingredients are well combined.
In a large bowl, beat egg. Add milk, oil, vanilla and mashed bananas. Sir to mix ingredients until well combined.
Add flour mixture to the banana mixture and stir until ingredients are incorporated, do no over stir.
Line a 12 muffin pan with 12 muffin tins or spray muffin tin generously with cooking spray.
Divide batter evenly among the 12 muffin tins.
Add a teaspoon of Nutella to the top of each muffin and gently cut Nutella into batter with a knife or toothpick to produce pretty swirls.
Bake at 375 degrees for 17-20 minutes or until toothpick comes out clean.