Bryant's Banana Bread

In a mixer cream 3/4 C room temp. butter, 1C sugar and 1/2 C brown sugar. Add 2 room temp. eggs and 1 tsp. vanilla, beat until smooth. In a separate bowl sift together 1 tsp. baking soda, 1/2 tsp. baking powder, 1/4 tsp. salt and 2 1/2 C all purpose flour. Alternately add dry ingredients to mixer with 1 1/4 C sour cream. Add 4 small mashed bananas and if you want to add 1/2 C chopped walnuts. Bake in 2 greased loaf pans for 60 minutes at 350 degrees F or until a toothpick in the center of the loaf comes clean.