In a large skillet, sear the beef in 6 tablespoons oil. Add the onion, celery, 2 ounces of the carrot, 2 cloves of the garlic and caramelize. Add tomato paste, stock, and bay leaves. Simmer and let cook until meat is tender, about 1 hour. If meat is not tender, continue cooking, checking every 30 minutes. Meanwhile, preheat the oven to 350 degrees F. Toss the tourneed carrots, celeriac, and turnip with oil. Roast until tender, about 40 minutes.
In a separate saucepan, saute the mushrooms and thyme in oil, until the mushrooms have given up most of their liquid and are tender. Add the mushroom mixture to the stew. Serve beef with roasted vegetables.