Preheat oven to 350 degrees. Prepare two loaf pans by spraying with cooking spray. Place parchment in each pan so it sticks up over each long side. These will be your ‘handles’ to pull out the loaf when cooled. Press parchment to stick to sides of pan and spray again. Set aside.

Sift flour, baking soda, salt and baking powder into a medium bowl and set aside.

Mix mashed bananas, yogurt, butter, warm water, and vanilla in large bowl. Add eggs and egg white one at a time to banana mixture, stirring continuously. Add sugar and mix well by hand. Do not use a mixer!

Add dry ingredients 1 cup at a time, stirring continuously.

Pour mixed ingredients into two prepared pans and sprinkle chopped walnuts over top of each loaf. Bake 50–55 minutes. Remove from oven when a few crumbs still cling to a tester. Let cool in pan 10 minutes before removing loaves to a cooling rack.