Preheat oven to 350, spray a 9x5x3 loaf pan
Beat butter in large bowl with electric mixer at medium speed until light and fluffy.
Add sugar, brown sugar, beat well
Add egg, whites and vanilla, until well blended.
Add mashed bananas and beat on high speed 30 seconds.
Combine flour. baking soda, salt and baking powder in medium bowl. Add flour mixture to butter
mixture alternately with cream, ending with flour mixture. add walnuts and mix well.
Pour batter evenly into prepared loaf pan. Bake until browned and toothpick inserted near center comes out clean, about 1 hour 15 min.
Cool bread in pan on wire rack 10 minutes Remove bread from pan, cool completely on wire rack