Spread the walnuts on a cutting board and smash them using the bottom of a measuring cup or jar. Combine all walnut crumble ingredients in a medium bowl. Using clean hands, blend the ingredients together until the butter is completely incorporated. Squeeze handfuls of the crumble in your hands, then break apart the bigger clumps to form pieces resembling a coffeecake topping.
Preheat the oven to 350˚F. Lightly grease a loaf pan with butter.
Put the bananas in a large bowl, and use a fork to mash them. Mix in the melted butter, sugar, egg, vanilla, brandy, and the spices. Sprinkle the baking soda and salt over the top and mix it in. Add the flour, and mix until just incorporated.
Pour into the buttered loaf pan. Spread the crumble topping evenly over top.
Bake for 50 minutes to an hour, or until a toothpick comes out clean. Cool before slicing and serving.
Recipe by Spoon With Me at https://spoonwithme.com/whole-wheat-banana-bread-with-walnut-crumble/