Grease 9" x 5" loaf pan.
Beat together butter and sugar.
Add eggs. Mix well.
Add sour cream, flour, baking soda, vanilla, and bananas. Mix well.
Pour into prepared loaf pan.
Bake at 350 degrees F for 45 - 55 minutes, or until toothpick in center comes out clean.
Cool on rack, and wrap in plastic wrap overnight to bring out the moisture in the bread.
Makes 1 loaf, cut into 14 slices about 5/8" thick each.