Preheat oven to 180°C. Toss lamb shanks in seasoned flour to coat. Shake off any excess. Heat oil in a large ovenproof casserole over medium-high heat. Cook lamb shanks, turning often, for 8 minutes or until well browned all over. Reduce heat to medium. Add carrot, celery, garlic and bay leaves. Cook, stirring, for 5 minutes.
Combine soup mix, stock, tomato paste and parsley in a jug. Stir into pan with barley and 1 cup water. Cover and bring to the boil. Transfer to oven and cook for 2-3 hours or until meat is very tender.