Sift together flour, baking soda, and salt.

Using an electric mixer beat the sugar and butter until fluffy. Add the eggs, then the vanilla. Beat until well combined. Stir in the flour, baking soda, and salt. Fold in the mashed bananas until just combined. Stir in walnuts.

Spread one third of the batter evenly into the bottom of the prepared pan. Spoon one third of a cup of Nutella over the batter in the pan and then swirl through the batter with a table knife. Place one third of the remaining batter evenly over the first layer and swirl with one third of a cup of the remaining Nutella. Spread the remaining batter evenly over the top and top with the remaining one third of a cup of Nutella. Swirl through the batter with a table knife.

Place loaf pan on a baking sheet and bake for 60-70 minutes or until golden brown and a toothpick inserted in the center comes out clean. Let the bread cool in the pan for at least 30 minutes before removing to a wire rack to cool completely.

Do not slice banana bread until completely cool---at least 3 to 4 hours or overnight.

NOTE: Sometimes after the bread is cooled, I chill it in the refrigerator for a couple of hours. This helps the Nutella harden a bit and makes for a less messy eating experience. Either way it is delicious!