Pat dry the veal shanks with paper towels to remove any excess moisture. Veal shanks will brown better when they are dry.
Secure the meat to the bone with the kitchen twine (only if necessary).
Sprinkle veal with salt and freshly ground pepper.
Dredge the shanks in flour, shaking off excess. Dredge a second time.
In a large, deep heavy pot, heat the olive oil; do not burn. Use a pot with a fitted lid.
Add the garlic.
Add veal shanks to the hot pan and brown all sides, about 3 minutes per side.
Do not burn the garlic while browning the veal; if this happens, remove the garlic immediately.
Remove browned shanks and set aside.
In the same pot of olive oil and garlic, add the onion, carrot, celery, and parsley.
Season with salt at this point to help draw out the moisture from the vegetables.
Saute until soft and translucent, about 8 minutes.
Return browned shanks to the pan and add the wine and reduce liquid by half, about 5 minutes. Add the chicken broth and the bouquet garni.
Add the tomato sauce/passata and mix well.
Reduce heat to low, cover pan, and simmer for about 2 hours or until the meat is falling off the bone.
Check every 15 minutes, turning shanks and adding more chicken stock and/or tomato sauce/passata if necessary.
The level of cooking liquid should always be about 3/4 the way up the shank.
Carefully remove the cooked shanks from the pot and place them on a serving platter.
If you used kitchen twine, cut it off and discard it.
Remove and discard the bouquet garni from the pot.
Pour all the juices and sauce from the pot over the shanks.
Garnish with chopped parsley and lemon zest gremolata.