Combine first 3 ingredients in a bowl, beating at medium speed of an electric mixer. Add banana; beat well. Add eggs, 1 at a time, beating after each addition. Combine flour and soda; add to sugar mixture alternately with milk, beginning and ending with flour mixture. Mix after each addition. Stir in vanilla. Reserve 1-1/2 cups batter, and set aside. Combine 1 cup batter, syrup and cocoa; stir well. Pour remaining light-colored batter into a 12-cup Bundt pan coated with cooking spray. Spoon chocolate batter over batter in pan. Pour reserved light-colored batter over chocolate batter. Bake at 350 degrees for 45 minutes or until a wooden pick inserted in center comes out clean. Cool in pan 10 minutes; remove from pan. Cool on a wire rack. Combine powdered sugar and next 2 ingredients; stir well. Drizzle over cake. Yield: 16 servings (serving size: 1 slice). 234 calories (18% from fat), 4.6 g fat (1 g sat, 1.3 g mono, 1.8 g poly), 27 mg cholesterol and 98 mg sodium.