Braised Brisket With Pearl Onions and Carrots

Place rack in lower third of oven and preheat to 450°F. Season one 5-pound flat-cut beef brisket, fat trimmed all over with kosher salt and freshly ground black pepper. Heat 2 Tbsp. extra-virgin olive oil in Dutch oven or other heavy large sauté pan over medium-high heat. Cook brisket until browned, about 5 minutes per side. Transfer to large roasting pan.

Return sauté pan to stovetop and add 7 cups finely chopped onions (3–4 large onions), 1 cup finely chopped carrot (from about 2 medium carrots), 1 cup finely chopped celery (about 3 stalks), and 2 Tbsp. chopped garlic (from about 1 head of garlic). Cook, stirring occasionally until browned and starting to soften, 8–10 minutes. Pour in two 750-ml bottles dry red wine; using wooden spoon, scrape any browned bits from bottom of pan. Add 8 large fresh thyme sprigs, and 2 bay leaves and bring to boil. Simmer until liquid is reduced to 5 cups, 10–12 minutes. Add 8 cups homemade chicken stock or low-sodium beef broth and return to boil. Pour wine mixture over brisket to fill two thirds of roasting pan; reserve remaining wine mixture.

Transfer brisket to oven and braise, uncovered, until very tender, turning and basting occasionally and adding more wine mixture as necessary to keep pan two-thirds full, about 3½ hours.

Transfer brisket to platter. Strain pan juices into 4-cup measuring cup, pressing on solids. Discard solids. Add enough reserved wine mixture to measure 3½ cups. Season jus with kosher salt and freshly ground black pepper.

Heat remaining 1 Tbsp. extra-virgin olive oil in large skillet over medium heat. Add 1 lb. young carrots, peeled, 12 oz. pearl onions, blanched, peeled, and 1 Tbsp. chopped fresh thyme; cook, stirring occasionally, until golden, about 5 minutes. Cover and cook until vegetables are crisp-tender, about 5 minutes. Season with kosher salt and freshly ground black pepper.

Thinly slice brisket against the grain and serve with red wine sauce and cooked carrots and pearl onions. Do ahead: Brisket be braised 1 day ahead. Cover meat and sauce separately in airtight containers; chill. Arrange meat in baking dish. Cover with aluminum foil; reheat in 350° oven until warmed through about 40 minutes. Rewarm sauce.