Step by step

Pre-heat the oven to 200°C, line a loaf tin with baking parchment, and pour in the first half of the cake mix. Then add the Nutella cake mix on top

If you want to make your banana and Nutella bread even more yummy, add either walnuts or hazelnuts which will provide an extra bit of texture.
Banana and Nutella bread is a sponge cake whose origin is clearly to be found in Anglo-Saxon countries, especially the United States and Australia.