In a Dutch oven, combine beef, turkey, onion, carrot, celery, and garlic; cook until meat is brown and onion is tender. Drain off fat. Stir beef broth, undrained tomatoes, 1 tablespoon sage, thyme, rosemary, salt, and pepper into beef mixture in Dutch oven. Bring to boiling; stir in potatoes. Reduce heat. Cover and simmer for 10 to 15 minutes or until vegetables are tender. If desired, garnish with additional fresh sage.