Horseradish-Glazed Brisket and Short Ribs with Root Vegetable Mash

Ingredients

• 3.5 pound flat-cut beef brisket 
• 0.3 teaspoon peppercorns whole black
• 2 pounds beef short ribs bone-in ( 6 medium)
• 2  cardamom pods 
• 1 cup celery leaves 
• 4 cups cubes celery root peeled (celeriac; 1 large)
• 1 tablespoon coarse kosher salt 
• 3 tablespoons dijon mustard 
• 1  garlic clove peeled
• 3 tablespoons brown sugar packed ()
• 3 tablespoons horseradish white prepared
• 1 medium onion peeled
• 4 cups cubes rutabaga trimmed peeled ( 2 large)
• 2  turkish bay leaf 
• 0.3 cup butter unsalted room temperature ()

Equipment

• oven
• pot
• potato masher
• glass baking pan
• cheesecloth

Directions

1. Stack three 8-inch squares cheesecloth onwork surface.
2. Place celery leaves and next5 ingredients in center of square. Gatherup edges of cheesecloth; tie with kitchenstring and set packet aside.
3. Place brisket and short ribs in heavylarge wide pot.
4. Add enough water topot to cover meat. Bring to simmer overmedium heat. Skim any impurities thatrise to surface. Reduce heat to maintaingentle simmer.
5. Add packet, onion, and 1tablespoon coarse salt. Cover; simmer untilmeat is fork-tender, about 2 hours for shortribs and 3 1/4 to 3 1/2 hours for brisket.
6. Transfermeats to 15x10x2-inch glass baking dish.
7. Remove and discard bones from short ribs.
8. Remove and discard packet and most ofonion from cooking liquid. DO AHEAD: Can bemade 1 day ahead. Cool cooking liquid andmeats slightly, then chill separately untilcold. Cover each; keep chilled.
9. Bring meat cooking liquid to boil; addcelery root, rutabaga, and potatoes. Reduceheat to medium and cook uncovered untilvegetables are tender, about 45 minutes.
10. Drain vegetables, reserving 3 cups cookingliquid. Return vegetables to pot and stir overlow heat 1 minute to dry. Mash vegetableswith potato masher to coarse puree. Mash inbutter. Season to taste with salt and pepper.DO AHEAD: Can be made 2 hours ahead.
11. Let stand at room temperature. Rewarmover medium-low heat before serving,adding reserved meat cooking liquid bytablespoonfuls as needed to moisten.
12. Preheat oven to 375°F.
13. Whiskhorseradish, mustard, and sugar in smallbowl.
14. Brush 3 tablespoons horseradishsauce over meats in dish.
15. Sprinkle with saltand pepper. Roast meats until browned andheated through, 35 to 45 minutes.
16. Transfermeats to work surface. Thinly slice acrossgrain.
17. Place on platter.
18. Drizzle 2 cupsreserved cooking liquid around.
19. Serve withvegetable mash and horseradish sauce.