Prepare polenta according to packet instructions, finish off with the butter, parmesan cheese and truffle oil. Pour into a lined baking sheet and allow cooling completely. In a large frying pan seal the pork cheeks in hot olive oil until browned on all sides. Remove the pork from the pan and cook the bacon and vegetables until browned, pour in the beer. Add the pork and simmer for 5 minutes. Stir in the veal stock. Transfer to a baking dish, cover with foil and cook gently for 2 hours in a moderate oven. When pork is tender remove from the sauce, pour the sauce into a sauce pan and reduce until thickened. Cut discs of the polenta with pastry cutter. Shallow fry, grill or bake until golden. Serve the pork together with the polenta, drizzle with sauce and rocket leaves. Drizzle lightly with truffle oil.