Season the veal shanks with salt and pepper and lightly dust each side with flour. Heat a large Dutch oven over medium-high heat, add the olive oil and brown the veal shanks on all sides. Remove the browned veal shanks to a paper towel lined plate.
Add the onion, celery and carrots to the hot pan and cook the vegetables over a medium high heat until they are a golden brown, stirring occasionally so the vegetables do not stick to the bottom of the pan, about 6 minutes. As the vegetables are browning add the garlic. Once the vegetables have reached a golden color add the tomato paste and cook for 4 minutes. Deglaze the pan using the white wine, being sure to scrape all of the brown bits off the bottom using a wooden spoon. Add the crushed tomatoes, spices, and bouquet garni. Add the veal shanks back to the pan and enough beef broth to come half way up the sides of the veal. Cover with a lid and cook for about 3 hours, turning occasionally and adding more stock, as necessary, to keep the veal partially submerged, until the veal shanks are very tender and the meat is falling off of the bone. Season with salt and pepper, to taste.
Meanwhile, make the gremolata by combining the crushed garlic with the lemon zest and the chopped parsley. Season with salt to taste.
Once the veal shanks are tender, remove the shanks from the cooking liquid and, when cool enough to handle, pull the meat from the bone and shred into small pieces. Discard the bones and return the pulled meat to the sauce. Taste and reseason the sauce, if necessary.
Cook the pappardelle in a large pot of salted, boiling water until al dente.
Serve the pappardelle with the ragu and garnish with the gremolata and the shaved Parmesan.