To cure the pork, combine 2 tablespoons of the salt with the sugar and ground mustard. Rub the mixture all over the meat, cover, and set it in the refrigerator to cure for 6 hours. Place a rack in the middle position and heat the oven to 325 F.

To roast the pork, rinse it under cold running water to remove the seasoning. Pat dry with paper towels. Combine the Dijon mustard, mace, black pepper, paprika and the remaining 1 tablespoon salt. Rub the mixture all over the meat. Set the pork in a roasting pan, cover tightly with aluminum foil and cook until the internal temperature reaches 175 F, about 45 minutes. Allow the meat to cool completely before slicing.

To make the sandwiches, heat a sandwich press or griddle to medium-high. Split the bread lengthwise and pull it open. Spread the mustard on 1 side of each roll and layer on the roast pork, ham, cheese and pickles. Spread the butter all over the outside of the sandwiches and griddle until the cheese is melted and the meats are warmed through, 3 to 4 minutes. (Alternatively, wrap the sandwich in foil and toast in a 350 F oven for 5 to 7 minutes.) Slice each in half on the diagonal and serve.