Moist, decadent banana bread swirled with gobs of rich, creamy Nutella and topped with crunchy, hazelnut streusel.
To make the streusel: In a medium bowl, whisk together flour, sugar, and cinnamon. Add butter and mix with your fingertips until the mixture lumps into unevenly sized crumbs. Add hazelnuts and mix. Refrigerate until ready to use.
Preheat oven to 325°F/160°C. Grease a 9x5-inch loaf pan.
To make the cake: Place bananas in a large bowl and mash them well using a fork or potato masher. Add oil, sugar, eggs, and vanilla extract, and mix until combined. Add the other ingredients, except for Nutella, to the bowl, and whisk just until combined. Set bowl aside.
Bake until a toothpick inserted into the center comes out clean, about 1 hour and 20 minutes (it sounds like a long time, but this is a big cake and it will take some time to fully bake). To prevent the top from browning too much, you can cover the pan loosely with aluminum foil after about 50-60 minutes of baking. Allow the cake to cool completely on a wire rack.
Recipe adapted from Bake from Scratch magazine, Recipe by Laura Crandall