Prepare the Veal:

Season the veal shanks with salt and pepper. Dredge each shank in flour, shaking off any excess.
In a large skillet or Dutch oven, heat the olive oil over medium-high heat. Add the veal shanks and brown on all sides, about 3-4 minutes per side. Remove from the skillet and set aside.

Sauté the Vegetables:

In the same skillet, add the onion, carrot, celery, and garlic. Sauté until the vegetables are softened, about 5 minutes.

Deglaze and Braise:

Add the white wine to the skillet, scraping up any browned bits from the bottom. Simmer until the wine is reduced by half.
Return the veal shanks to the skillet. Add the stock, diced tomatoes, bay leaf, and thyme. Bring to a simmer.
Cover and simmer gently over low heat for about 1.5 to 2 hours, or until the meat is very tender.

Prepare the Gremolata:

In a small bowl, combine the lemon zest, minced garlic, and chopped parsley.

Serve:

Once the veal is tender, transfer the shanks to serving plates. Spoon the sauce over the meat and sprinkle with the Gremolata.

Garnish and Enjoy:

Serve the Osso Buco with risotto, polenta, or mashed potatoes for a complete meal.