Preheat the oven to 300 F. Grease and flour two 9x5 inch loaf pans.
In a large mixing bowl, cream together butter and sugars. Add vanilla, bananas and eggs and mix until smooth. Sift together flour, salt and baking soda. Add dry ingredients to wet, and stir until just combined. Be careful to not overwork. Fold in nuts, if desired.
Divide the batter evenly between prepared loaf pans. Bake in preheated oven for 60 to 65 minutes until a toothpick or cake tester inserted into the center of the loaf comes out clean. Cool loaves in pans on a wire rack for 15 minutes. Remove from pans and cool on wire rack until completely cool.