Preheat oven to 325 degrees F. Season beef with salt and pepper. Heat oil and schmaltz in a 12-inch skillet over medium-high heat. Add meat and brown well on both sides. Remove from skillet to a 3-quart baking dish or nonreactive roasting pan; set aside. Add onions and garlic to skillet. Cook and stir until onions are translucent, about 5 minutes. Stir in celery heart, bay leaves, tomatoes, stock, wine, and tomato paste. Bring to boiling; boil gently, uncovered, for 2 to 3 minutes. Pour mixture around meat in dish. Cover with parchment paper, then tightly with a double thickness of foil. Roast for 3 to 3 1/2 hours more or until meat is tender. Remove meat from baking dish and transfer to a cutting board. Cover and let stand for 15 minutes.
For sauce, skim fat from cooking liquid. Discard bay leaves. Bake, uncovered, for 10 to 15 minutes more or until it reaches desired consistency. Slice meat across the grain. Serve with tomato mixture and top with parsley and horseradish. Serve with Ginger Pickled Onions.
Ginger Pickled Onions
Combine the vinegar, brown sugar, salt, and ginger in a nonreactive saucepan. Bring to a rapid simmer, stirring occasionally until sugar is dissolved. Simmer, uncovered, for 5 to 7 minutes or until syrupy. Add onion rings and simmer 1 minute more. Remove from heat and allow to cool completely.