Preheat oven 350' Spray bottom only of 9x5x3 inch loaf pan.
Beat butter in a large bowl with an electric mixer set at medium speed until light and fluffy. Add sugar and brown sugar, beat well. Add egg, egg whites and vanilla; beat until well blended. Add mashed banana and beat on high speed 30 seconds.
Combine flour, baking soda, salt, and baking poder in medium bowl. Add flour mixture to butter mixture alternately with cream, ending with flour mixture. Add walnuts to batter; mix well.
Pour batter evenly into loaf pan. Bake 1 hour 15 min. until browned and toothpcik inserted comes out clean.
Cool bread in pan on wire rack 10 min. Remove bread from pan; cool completely on wire rack. Slice and serve with butter and jam.
Best if wrapped in plastic wrap and left on counter over night for flavors to develop.