Preheat the oven to 350 degrees Fahrenheit.
Puree the bananas in your blender and measure out 1 1/2 cups to a bowl.
Add in all remaining wet ingredients and whisk together until well combined.
To the same bowl, add in both flours and all remaining dry ingredients aside from the walnuts. Be sure to spoon and level the flour into dry measuring cups, don't scoop from the bag.
Mix everything together with a wooden spoon, just until no flour clumps remain.
Stir in the chopped nuts.
Transfer to a 9x5 loaf pan lined with parchment paper and top with additional chopped walnuts and a sprinkle of brown sugar.
Bake for 50-60 minutes, or until a toothpick comes out clean. 55 minutes is ideal in my oven, but all ovens are different. Avoid opening the oven while baking because this can prevent the bread from rising properly.
Once done, remove from the oven and let cool in the pan for 10 minutes, then lift out and transfer to a wire rack to finish cooling. It's important to let it cool completely before slicing to ensure it doesn't crumble. Enjoy!