Preheat oven to 350 degrees. Line a 9x5 loaf pan with parchment paper (or grease and flour bottom and sides) and set aside.
In a large bowl, add all wet ingredients: bananas (mash with a fork), granulated sugar, brown sugar, oil, eggs, milk, and vanilla extract. Stir until well combined. Set aside.
In a separate bowl, whisk (or sift) together the dry ingredients: flour, baking soda, baking powder, cinnamon, and salt. Make a well in the middle and pour wet ingredients into dry ingredients. Stir until just combined. Fold in walnuts.
Pour batter into loaf pan. Cover loaf pan lightly with foil (remove foil halfway through baking. This ensures that the top of your bread doesn't burn.) Bake for 60-70 minutes, or until a toothpick comes out clean.
Banana nut bread freezes well and can be kept in the freezer for 3 months. Cover with aluminum foil and place in a freezer bag for optimal results.