How to Make It
Combine mushrooms and 2 cups of the stock in a saucepan. Bring to a boil over high; remove from heat, and let stand 45 minutes to 1 hour.
Meanwhile, heat oil in a large Dutch oven over high. Sprinkle beef with 1 teaspoon of the salt. Cook beef in hot oil, turning occasionally, until browned on all sides, 8 to 10 minutes. Remove from Dutch oven. Add onion, thyme, and garlic to Dutch oven, and cook, stirring and scraping to loosen browned bits from bottom of Dutch oven, until onion is translucent, 3 to 4 minutes. Add remaining 6 cups stock, and bring to a boil. Reduce heat to medium-low, and add browned beef. Cover and simmer 45 minutes.
Pour mushroom mixture through a fine wire-mesh strainer into a bowl, reserving liquid. Finely chop mushrooms.
Add barley, chopped mushrooms, reserved mushroom liquid, and remaining 1 teaspoon salt to beef mixture. Increase heat to medium-high, and return to a boil. Reduce heat to medium-low, and simmer 30 minutes. Add rutabaga and carrots, and simmer until barley, vegetables, and beef are tender, 20 to 25 minutes. Add Brussels sprouts and pepper, and cook until Brussels sprouts are just tender, about 5 minutes. Sprinkle servings with parsley.