1. Combine butter and sugar until creamy. Add eggs one at a time. Add vanilla and mix well.
2. In a separate bowl, sift together flour, soda and salt. Add dry ingredients to the wet ingredients and mix well. Add banana, sour cream and nuts. Mix until combined.
3. Bake in a pre-heated 350 degree Fahrenheit oven for 1 to 1 1/2 hours. Cool in the pan on a wired rack.
Yield: One 9inch loaf