How to Make It
Preheat oven to 350°.
Combine sugar and butter in a bowl; beat with a mixer at medium speed until well blended. Add banana, milk, sour cream, and egg whites.
Weigh or lightly spoon flour into dry measuring cups; level with a knife. Combine flour, baking soda, and salt, stirring with a whisk. Add flour mixture to banana mixture; beat just until blended (do not overbeat). Spoon batter into a 9 x 5-inch metal loaf pan coated with cooking spray. Bake at 350° for 1 hour or until a wooden pick inserted in center comes out clean. Cool in pan 10 minutes on a wire rack; remove from pan. Cool on rack.
Place half-and-half and chocolate in a microwave-safe bowl. Microwave at HIGH for 1 minute or until chocolate melts, stirring every 20 seconds. Cool slightly; drizzle over bread.