HEAT oven to 350ºF.
BEAT egg, dressing and bananas in large bowl with whisk until blended. Mix all remaining ingredients except chocolate in separate bowl. Add to banana mixture; stir just until moistened.
POUR half the batter into medium bowl; stir in chocolate. Spoon batters alternately into 9x5-inch loaf pan sprayed with cooking spray; swirl gently with knife.
BAKE 1 hour to 1 hour 5 min. or until toothpick inserted in center comes out clean. Cool in pan 10 min.; remove from pan to wire rack. Cool completely.