Preheat the oven to 350˚F. Lightly grease a loaf pan and set aside.
In the bowl of a stand mixer, cream together the butter and sugar until light and fluffy. Mix in the egg.
Mix in the flour and the salt into the sugar mixture until fully incorporated.
In a small bowl, disolve the baking soda in the water. Add to the batter and mix well.
Add in the banana and chocolate chips and mix until fully combined.
Pour the mixture into the prepared loaf pan.
In a microwave safe bowl, melt the Nutella. Spoon the Nutella over the batter and swirl with a knife.
Bake in the preheated oven for 50-60 minutes, or until a toothpick inserted comes out clean.