Preheat oven to 325˚F.
Pat shanks dry and season with salt and pepper. Sprinkle flour over to coat all sides, shaking off excess.
Heat oil in Dutch oven over medium heat and add mirepoix and garlic. Cook, stirring until onions are pale golden, about 5 minutes. Remove to plate.
Add the shanks to the Dutch oven and sear on all sides to a golden brown. Remove to plate.
Return mirepoix to Dutch oven. Add white wine, chicken broth, tomatoes, and herbs to the Dutch oven. Bring to a boil, stirring, and then turn the heat down to a simmer. Add shanks in one layer and juices back to the Dutch oven.
Cover the Dutch oven with a piece of parchment paper and cover pot with the lid.
Place the Dutch oven in the middle of the oven. Braise shanks until very tender, about 2 1/2 hours.
Remove the twine from the shanks. Discard the parsley sprigs and bay leaf.
Make the gremolata: Stir the ingredients in a small bowl.
Place one veal shank on each serving plate. Spoon the sauce over each one, then sprinkle the gremolata evenly over each veal shank.