Place lamb and stock in a large pot. Add salt and simmer for 1 hour. Saute onion, carrot, celery, garlic, marjoram and cumin in butter for 10 minutes. Add to the lamb, along with peas, beans, squash and corn. Simmer for 10 minutes. Add potatoes and rice. Simmer for 20 more minutes. Beat egg with milk, remove stew from heat and stir in milk mixture. Sprinkle with parsley and serve.