To keep the meat attached to the bone during the long simmering process, tie a piece of twine around the thickest portion of each shank before it is browned. Use a zester, vegetable peeler, or paring knife to remove the zest from a single lemon, then mince it with a chef's knife. With the lid on the pot cracked, the braising liquid should reduce to a sauce-like consistency in the oven. Just before serving, taste the liquid and, if it seems too thin, simmer the liquid on the stovetop as you remove the strings from the osso buco and arrange them in individual bowls.
4 tablespoons vegetable oil
6 veal shanks , 1 1/2 inches thick (8 to 10 ounces each), patted dry with paper towels and tied around the equator with butcher's twine
table salt and ground black pepper
2 1/2 cups dry white wine
2 medium onions , cut into 1/2-inch dice (about 2 cups)
2 medium carrots , cut into 1/2-inch dice (about 1 1/2 cups)
2 medium ribs celery , cut into 1/2-inch dice (about 1 cup)
6 medium cloves garlic , minced or pressed through a garlic press (about 2 tablespoons)
2 cups low-sodium chicken broth
2 bay leaves , small
1 can diced tomatoes (14.5 ounces), drained
3 medium cloves garlic , minced or pressed through a garlic press (about 1 tablespoon)
2 teaspoons grated lemon zest
1/4 cup minced fresh parsley leaves
1. FOR THE OSSO BUCO: Adjust an oven rack to the lower-middle position and heat the oven to 325 degrees. Heat 1 tablespoon of the oil in a large ovenproof Dutch oven over medium-high heat until shimmering. Meanwhile, sprinkle both sides of the shanks generously with salt and pepper to taste. Swirl to coat the pan bottom with the oil. Place 3 shanks in a single layer in the pan and cook until they are golden brown on one side, about 5 minutes. Using tongs, flip the shanks and cook on the second side until golden brown, about 5 minutes longer. Transfer the shanks to a bowl and set aside. Off the heat, add 1/2 cup of the wine to the Dutch oven, scraping the pan bottom with a wooden spoon to loosen any browned bits. Pour the liquid into the bowl with the browned shanks. Return the pot to medium-high heat, add 1 more tablespoon of the oil, and heat until shimmering. Brown the remaining shanks, about 5 minutes for each side. Transfer the shanks to the bowl. Off the heat, add 1 cup of the wine to the pot, scraping the bottom to loosen the browned bits. Pour the liquid into the bowl with the shanks.
2. Set the pot over medium heat. Add the remaining 2 tablespoons oil and heat until shimmering. Add the onions, carrots, celery, 1/4 teaspoon salt, and 1/8 teaspoon pepper and cook, stirring occasionally, until soft and lightly browned, about 9 minutes. Add the garlic and cook until lightly browned, about 1 minute longer. Increase the heat to high and stir in the broth, remaining 1 cup wine, accumulated veal juices in the bowl, and bay leaves. Add the tomatoes; return the veal shanks to the pot (the liquid should just cover the shanks). Bring the liquid to a full simmer. Cover the pot, cracking the lid just slightly, and transfer the pot to the oven. Cook the shanks until the meat is easily pierced with a fork but not falling off the bone, about 2 hours. (Can be refrigerated for up to 2 days. Bring to a simmer over medium-low heat.)
3. FOR THE GREMOLATA: Combine the garlic, lemon zest, and parsley in a small bowl. Stir half of the gremolata into the pot, reserving the rest for garnish. Season with salt and pepper to taste. Let the osso buco stand, uncovered for 5 minutes.
4. Using tongs, remove the shanks from the pot, cut off and discard the twine, and place 1 veal shank in each of 6 bowls. Ladle some of the braising liquid over each shank and sprinkle each serving with the remaining gremolata. Serve immediately