Ask your butcher to bone the loin and remove the rind, but keep both bones and the rind for the cooking.
If you are using dried cepes, cover them with warm water and leave to soak for 30 minutes or until they are soft. Drain, reserving the liquid.
Preheat the oven to 325 degrees F.
Lay the meat on a board and season well with salt and pepper. Cut the truffles or cepes into little pieces and lay at intervals along the meat interspersed with slivers of garlic. Roll the meat up and tie it with string into a long bolster shape. Place it in a roasting pan surrounded by the bones and the rind cut into strips. Roast the preheated oven for 30 minutes. Pour in the hot stock or water, the wine, and the liquid from the cepes. Cover and cook for a further 2 to 2 1/2 hours.
Remove the pork and keep hot. Strain the juices and reduce, then season to taste. Serve with the sliced pork. Or, if serving the pork cold, pour off the juices into a bowl and chill. Remove the fat, but keep it for frying bread or little potatoes--it has a splendid flavor. The juices will have jellied and should be chopped and arranged around the cold pork in a serving dish. Serve with what you will, such as a fine salad and some sauteed potatoes.