Preheat oven to 350 degrees. Grease and flower two 9 by 5 by 3 inch loaf pans or several smaller pans.
Cream two cups of sugar and one cup of margarine with with an electric mixer. Add six very ripe mashed bananas together with four well-beaten eggs. In a separate bowl, sift together two and one-half cups of cake flour, a teaspoon of salt and two teaspoons of baking soda. Mix the flour mixture into the banana mixture using a spatula or wooden spoon. Do not over-mix. Stir in three-quarters cup of chopped walnuts (this ingredient is optional).
Spoon the batter into the prepared pans. Fill each half to two thirds full. Cook at 350 degrees for about 55 minutes, or until a toothpick comes up dry after testing the center of the loaf. Turn out immediately onto a cake rack to cool.