In a large mixer bowl combine 1 cup of the flour, the sugar, baking powder, baking soda, and salt. Add mashed banana; softened butter, and milk. Beat with an electric mixer on low speed till blended, then on high speed for 2 minutes.
Add eggs and remaining flour beat till blended. Stir in nuts. Pour batter into a greased 8x4x2-inch loaf pan.
Bake at 350 degrees for 55 to 60 minutes or until a toothpick inserted near the center comes out clean.
Cool for 10 minutes on a wire rack. Remove from pan; cool thoroughly on a wire rack. Wrap and store overnight before slicing.