Mosefund Farms of Branchville, New Jersey produces herb-cured lardo from their Mangalista pigs. It is cured pure pork fat from the belly, below the cut used for bacon. It can be thinly sliced like prosciutto; look for similar products in butcher shops or gourmet markets. If you can't find slab lardo, you can also use whipped lardo to spread on the toasted bread, or substitute any thinly sliced cured meat, such as coppa, prosciutto, or salami.