Preheat oven to 350 °F
In a large mixer bowl, combine 1 cup of the flour, the sugar, baking powder, baking soda, and salt.
Add mashed banana, butter, and milk, then beat with an electric mixer on low speed until blended, then on high speed for 2 minutes.
Add eggs and remaining flour, then beat until blended. Stir in nuts.
Pour batter into an 8 inch loaf pan, that has been coated with a non-stick spray, and bake 55 to 60 minutes, or until a toothpick inserted into the center comes out clean.
Allow to cool for 10 minutes on a wire rack before removing the bread from the pan. Place loaf on the rack and allow to cool completely.