Preheat oven to 350°. Spray a loaf pan with nonstick cooking spray.
Cooking spray
Mash bananas (4 small or 3 large) in a medium bowl. Peel and chop the other 2 bananas into small pieces.
6 small bananas
Sift the whole wheat flour, all purpose flour, baking powder, baking soda, and salt together in a separate bowl.
1 cup flour, 1 cup whole wheat flour, 2 teaspoons baking soda, 1 teaspoon baking powder, 1/2 teaspoon sea salt
In a large bowl beat the brown sugar and butter together, add the egg and beat until combined.
1/2 cup brown sugar, 2 tablespoons butter, 1 egg
Add the dry ingredients, the mashed banana and the milk to the butter mixture in batches, alternating between them and mixing in between each addition. Mix it until just combined.
1/4 cup skim milk
Fold in the walnuts and chopped bananas.
1/2 cup chopped walnuts
Pour batter into prepared loaf pan and bake for 50-60 minutes, or until the top of the loaf begins to brown and a toothpick, or tester, inserted into the center of the loaf comes out clean.
Cool for 15 minutes in the pan and then turn the loaf out onto a wire rack and allow to cool.