Arrange bread cubes in a single layer on a baking sheet. Bake at 350° for 5 minutes or until toasted. Remove bread from oven; decrease oven temperature to 325°.
Combine milk and next 5 ingredients (milk through egg) in a medium bowl, stirring well with a whisk. Add bread, tossing gently to coat. Cover and chill 30 minutes or up to 4 hours.
Divide half of bread mixture evenly between 2 (6-ounce) ramekins or custard cups coated with cooking spray; sprinkle evenly with half of chocolate. Divide remaining bread mixture between ramekins; top with remaining chocolate.
Place ramekins in an 8-inch square baking pan; add hot water to pan to a depth of 1 inch. Bake at 325° for 35 minutes or until set. Serve each pudding warm with 1 tablespoon whipped topping.