Make small incisions over the outer lining of the veal shunks. This will prevent the slices from curling during the cooking time.
Place the flour in a large bowl or shallow dish, and lightly flour the meat slices on both sides, shaking off the flour in excess.
Heat the extra-virgin olive oil in a large pot over medium-low heat, add the onion and cook until translucent, stirring often to prevent it from burning.
Add in the veal shanks and brown them on both sides.
Turn the heat to medium, pour in the white wine, and let it evaporate, about 3-5 minutes.
Pour in enough stock so that the meat is just half-submerged in the liquid. Season with sea salt and black pepper to taste. Lower the heat to a minimum, cover, and cook for about 1½ hours, adding a bit of broth when necessary, to keep the meat moist.
Right before you take the meat off the heat, prepare the gremolata. Finely chop together the garlic with the lemon zest and parsley, and mix all the ingredients together.
Remove the pot from the heat, top each slice of veal with the prepared gremolata, and serve with risotto alla milanese or your favorite side dish.