Melt butter in a 6-quart stockpot over medium heat. Add onion and garlic and saute until onion is translucent. Meanwhile, dredge veal cubes in flour, discarding any extra flour. When onions are translucent, add the veal to the stockpot and cook until lightly browned. Add mushrooms, parsley, crushed tomatoes, and chicken stock. Simmer for approximately 45 minutes, or until meat is fork-tender. Season with salt and pepper, to taste, and serve.