
Dredge meat in about 1 cup flour, coating roast lightly. In a Dutch oven or medium heavy stockpot, heat oil over moderate heat; brown roast, all sides, in hot oil. Season meat with salt and pepper to taste. Add garlic, chopped onion, beef broth or consommé, tomato sauce, wine, bay leaves, and thyme sprigs. Reduce heat, cover, and simmer over low to moderate heat for 2 hours. Add potatoes, carrots, parsnips, turnips, and celery; continue cooking, covered, for 45 to 60 minutes or until meat and vegetables are fork tender. Transfer meat to a plate and vegetables to a warm platter; cover vegetables and keep warm in a very slow oven (250 degrees F.) while preparing gravy. Remove bay leaves and thyme stems from pan liquid.
To prepare gravy, skim off fat from hot pan liquid. Add bouillon cubes to pan liquid. In a 1-cup measure, blend cold water into ½ cup flour with a wire whisk until smooth; stir flour mixture into pan liquid, blending well. Cook, stirring constantly, over moderate heat until gravy is slightly thickened and bubbly hot. Adjust seasoning to taste. Return meat to gravy; add boiling onions and continue to cook over low heat, uncovered, for 20 minutes.
To serve, cut roast across the grain into thin slices; arrange roast and boiling onions on the platter with vegetables. Garnish with sprigs of thyme and parsley or minced parsley. Pass gravy in a gravy boat.