½ cup butter at room temp
1 cup sugar
2 eggs
1 ½ cups unbleached flour
1 tsp baking soda
1 tsp salt
1 cup mashed very ripe bananas
½ cup sour cream
1 tsp. vanilla
½ cup chopped walnuts or pecans

Preheat oven to 350° F
generously butter a 9X5X3 inch loaf pan(I throw in fine bread crumbs and knock them all around to coat the pan.  I find they work better than flour)

Cream butter, sugar and eggs.
Sift dry ingredients and combine with butter mixture, blending well.
Add bananas, sour cream and vanilla, stirring well.  Stir in nuts and pour into pan.

Bake one hour.  Turn out of pan onto wire rack and let cool.