Combine first 5 ingredients in a large bowl; beat at medium speed of an electric mixer until well blended. Combine flour and next 3 ingredients; Add flour mixture to banana mixture, stirring just until moistened.

Spoon ½ batter into an 8 ½ x 4 ½ x 3-inch loaf pan coated with baking spray with flour. Add ¼ cup Nutella in dollops. Swirl a bit then top again with remaining batter. Add another ¼ cup Nutella in dollops on top. Swirl again.

Bake at 350º for 1 hour and 5 minutes or until a wooden pick inserted in center comes out clean. Cool 10 minutes in pan on a wire rack; remove from pan, and cool completely on a wire rack. (Bake mini loaves for 35 minutes or muffins for 18 minutes.)