If your pork comes with the skin on, remove the skin, and rub it generously with salt, wrap in paper towel, and place on a plate in the fridge.
Mix ingredients together in a large resealable bag. Add pork and let marinate overnight.
Preheat oven to 325F, place pork, along with some marinade in a roasting dish. Cook until the pork reaches 155F, about 30 minutes per pound of pork.
About 30 minutes before the pork is finished, remove the pork skin from the fridge, allowing it to come to room temperature.
Once pork has finished roasting, raise oven temperature to 500F, and place pork skin on a roasting dish, lightly covered with tinfoil (to prevent splatter), and roast until skin turns into crackling (gets puffy, crisp and golden brown).
Roughly chop up crackling and add to pork when placing on sandwich.
Slice bread in half, spread about a tablespoon of mustard on the inside of each side of bread.
Place enough ham to cover the bottom slice, followed by the roast pork and crackling, then your pickles, followed by swiss cheese, and your top slice of bread.
Get a pan on medium heat.
Spread butter on the outside your sandwich.
Grill the sandwich in your pan until golden brown on each side and cheese has melted. Using a flat surface, like the bottom of a baking dish, press down on the sandwich as it grills.
Slice and enjoy!