Preheat oven to 350 degrees F.
Spray 9×5-inch loaf pan with nonstick spray.
In a medium bowl, whisk together flour, baking soda & salt.
In a separate large bowl, cream sugar and butter together.
Add eggs, one at a time, beating well after each egg is added.
Add mashed bananas, milk and vanilla and beat until well combined.
Add flour mixture, beat at low speed just until flour is incorporated (don’t over mix).
In a small microwave save bowl, add Nutella and heat for 15 seconds. Stir to evenly mix heated Nutella. Add 1 cup of the banana bread batter to the Nutella and stir until well mixed.
Spoon Nutella batter alternately with plain banana bread batter into the prepared loaf pan. Swirl batters together with a knife.
Bake 50 to 60 minutes.
Cool in pan for at least 15 minutes and then remove loaf from pan and place on a wire rack to cool completely.