Heat 1 Tb. oil in large Dutch oven over low heat. Add meat and halved onion and brown on all sides, about 10 minutes. Pour in the water. Simmer, partially covered, about 2 hours; skim surface as needed. Remove meat to plate. Strain stock through sieve lined with dampened paper towel. (Soup can be prepared up to this point 1 day in advance.) Remove bone and gristle from meat; shred meat and add to strained stock. Heat remaining 1 Tb. oil in Dutch oven over low heat. Add chopped onions, carrots, and celery and stir to coat with oil. Cook covered, stirring occasionally, until tender, about 15 minutes; do not allow to brown. Stir in garlic, increase heat to medium, and cook 1 minute. Stir in mushrooms and cook 5 minutes longer. Add stock with beef, tomatoes, parsley, salt, pepper, allspice, and bay leaf. Heat to boiling and stir in barley. Reduce heat and simmer, partially covered, until barley is tender, about 45 minutes. If using spinach, stir into soup for last 5 minutes of cooking. Taste and adjust seasonings. Serve hot. Makes 3 quarts. Nutritional value: 120 cal, 7 g pro, 4 g fat, 14 g carb, 591 mg sod soup 31