6 (1- to 1 1/2-inch-thick) pieces osso bucco (beef shanks) (about 4 pounds total)
Kosher salt and freshly ground black pepper
1 cup all-purpose flour
1/4 cup extra-virgin olive oil, plus more if needed
1 large yellow onion, minced
2 medium carrots, minced
1 celery rib, minced
3 medium cloves garlic, minced
1 cup dry red wine, such as a cabernet sauvignon
1 cup low-sodium beef stock, plus more as needed
2 – 15oz cans fire roasted diced tomatoes
3 fresh thyme sprigs
1 bay leaf
2 tablespoons finely minced flat-leaf parsley leaves
Zest of 1 lemon
6 cloves of garlic, finely minced
Preheat oven to 325°F (163°C). Season the shanks all over with salt and pepper. If you have butcher's twine, you can tie a length of it tightly around the circumference of each shank to help hold their shape during cooking.
Add flour to a shallow bowl. In a large Dutch oven, heat olive oil over medium-high heat until shimmering. Working in batches, lightly dredge shanks all over in flour, shaking off excess, and add to Dutch oven. Cook shanks until lightly browned on both sides. Transfer browned shanks to a platter and repeat with remaining shanks; add more oil to Dutch oven at any point if it becomes too dry.
Add butter to Dutch oven, along with onion, carrot, celery. Cook, stirring, over medium-high heat until vegetables are softened and just starting to turn a light golden color, about 6 minutes. Add garlic and cook about 1 minute.
Add wine, stock, thyme, bay leaf, and tomatoes to Dutch oven, along with shanks and any accumulated juices. Try to arrange the shanks in as even a layer as possible (a little overlap is okay to make them fit). The liquid should nearly cover the shanks; if it doesn't, add more stock or water. Bring to a simmer.
Cover shanks with parchment lid and transfer to oven. Cook for 3 hours. If the pot becomes too dry, add more stock or water as needed to keep it moist; evaporation and reduction are good, but the pot shouldn't go dry. Feel free to move the shanks around so that any that are submerged can be exposed to the oven air.
In a small bowl, make the gremolata: stir together parsley, lemon zest, garlic and a pinch of salt. Use a fork to slightly mash the mixture together. Set aside.
During the last 20 minutes of cooking, stir in 1 to 2 teaspoons gremolata or to taste. Save the remainder for garnish.
Carefully transfer shanks to a platter. Skim any fat on the surface of the liquid off and either adjust the consistency using water or stock, or simmer the liquid until reduced to a thicker consistency. Discard thyme and bay leaf and season with salt and pepper if necessary.
Remove twine from shanks, if used. Serve shanks with vegetables and sauce on top of shanks. Garnish with a teaspoon of gremolata and provide a small spoon for guests to scoop out bone marrow.