Preheat oven to 350°F. Grease a 9-inch loaf pan. Line bottom and long sides with parchment, leaving a 1-inch overhang. Grease and flour.
Make cake: Beat eggs, sour cream and rum. Sift flour, baking powder, cinnamon and salt. With mixer, beat butter and sugars until light, 3 minutes. Add egg mixture in thirds and then banana. Fold in flour mixture and then chocolate.
Pour into pan and bake until a toothpick inserted in center comes out clean, 1 hour and 20 minutes. Let cool on a rack for 15 minutes. Lift cake from pan and let cool on rack.
Make topping: Whisk spread, sour cream and 1 Tbsp. water in a pan over medium heat until smooth. Drizzle over cake. Sprinkle with banana chips.