Preheat oven to 350°. Grease two loaf pans.
In a large bowl, combine 2 cups of flour, the sugar, baking powder, baking soda and salt.
Add the mashed banana, shortening, and creamer or milk. Beat with an electric mixer on low until combined, and then on high for 2 minutes.
Add the eggs and the rest of the flour. Beat until blended. Stir in nuts, if desired.
Divide the batter evenly between the two greased loaf pans and bake at 350° for 55 to 60 minutes. Check with a toothpick. If the toothpick comes out clean, the bread is done.
Cool in the pans on a wire rack for 10 minutes. Then remove from the pans and cool completely on the wire rack before wrapping and storing.