Preheat oven to 325 F. Parboil cabbage and drain. In a large bowl, combine cooked rice, onion, ground beef, ground pork/veal and egg. Pour 1/4 cup butter over mixture. Mix well with your hands. Core cabbages, separate leaves and cut thick ribs out of each leaf. Put a large tablespoonful of meat mixture in the center of each cabbage leaf. Fold in sides, roll up and place seam side down in large roasting pan. In large bowl, combine beef broth, tomatoes, tomato sauce, tomato soup and remaining 1/4 cup butter. Pour over rolls. Bake at 325 F or 1 1/2 hours. Baste with tomato mixture occasionally during baking.