Heat ¼ cup of the olive oil over medium heat in a heavy flameproof casserole pan large enough to hold the veal slices in a single layer. Season the veal with salt and pepper and coat the pieces with flour, shaking off any excess. When the oil is hot, add the veal pieces and cook over medium heat, turning once, until browned, 10 to 15 minutes. Remove the veal from the pan and set aside.
Pour off the fat from the pan, wipe it with paper towels, and add 3 tablespoons of olive oil. Heat the oil over medium-high heat and add the celery, carrots, onion, and mushrooms. Cook the vegetables, stirring frequently, until soft, about 15 minutes. Turn up the heat, add the wine, and boil, stirring constantly, until the wine has evaporated.
Stir in the crushed tomatoes and 2 cups of the hot stock. Carefully arrange the veal slices in the casserole and spoon some of the vegetable mixture over them. If the liquid does not cover the meat, add more stock. If you need more than 4 cups of stock to cover the meat, your pan is too big and you should transfer everything to a smaller casserole.
When the liquid comes to a boil, lower the heat, cover the casserole tightly, and simmer gently for 2 to 2½ hours, or until the meat is very tender when pierced with a fork. Uncover the casserole during the last 30 minutes of cooking to reduce the sauce a bit.
While the meat is cooking, chop the ingredients for the gremolata and combine them.
Ten minutes before serving, remove the meat to a deep serving platter and keep it warm. Boil the sauce to reduce it a bit more if it is still thin. Stir in the gremolata and simmer for 1 or 2 minutes. Then spoon the sauce over the meat. Serve atop Risotto Parmigiano or Risotto alla Milanese.