In a large bowl, stir together egg product or egg whites, crushed crackers, onion, catsup, 3 tablespoons of the soup mix, the poultry seasoning (if you like), and the 1/4 teaspoon pepper. Add ground beef and ground turkey; mix well.
Shape meat into an 8x4x2-inch loaf. Place in a shallow baking pan. Bake, uncovered, in a 350 degree F oven about 1 hour or until an instant-read thermometer inserted in center registers 165 degree F and juices run clear.
Meanwhile, place potatoes and carrots in a 4-quart Dutch oven. Pour broth over vegetables; stir in the remaining soup mix.
Bring to boiling; reduce heat. Cover and cook for 20 minutes. Add cabbage. Return to boiling; reduce heat. Cook, uncovered, for 10 minutes more or until vegetables are tender.
Remove vegetables; keep warm. Measure 1-1/2 cups cooking liquid; discard any remaining liquid. Stir together cornstarch and cold water. Stir into reserved liquid. Cook and stir until bubbly. Cook for 2 minutes more.
Serve with meat loaf and vegetables. Season to taste with pepper. Makes 6 servings.