Preheat the oven to 350F, and spray a 9x5 loaf pan with nonstick spray. Set aside.

In a medium bowl, mash the bananas with the oil, almond milk, and vanilla. Stir in the sugars until well combined, then add in the flours, baking soda, and salt, and mix until just combined.

Transfer half the batter in a separate bowl, add in the Nutella, and mix until well combined.

In a small bowl, prepare the streusel: combine all the ingredients and mix with a fork until small clumps form.

Pour about half of the streusel mixture into the batter without the Nutella, and fold gently to combine.

Using a spoon, dollop alternating spoonfuls batter into the prepared pan. With a clean spoon, place additional small dollops of Nutella across the top, then use a smooth knife to create swirls in the batter.

Top the banana bread with the remaining streusel, then bake in your preheated oven for about 45 minutes, uncovered.

If a toothpick inserted in the center still comes out gooey, cover the loaf with foil and bake for up to 20 minutes more. Let cool completely before slicing and enjoying!