In a bowl, combine 2 tablespoons of kosher salt, 2 tablespoons of granulated sugar, and 1 tablespoon of ground mustard. Rub this mixture generously all over the 3.5-pound boneless pork shoulder, ensuring even coverage. Wrap the seasoned pork in plastic wrap and refrigerate overnight.

Preheat your oven to 325°F (163°C). Rinse the pork under cold water and pat it dry with paper towels. Rub the pork shoulder with a mixture of ¼ cup coarse Dijon mustard, ¼ cup smooth Dijon mustard, 1 teaspoon ground mace, 2 tablespoons ground black pepper, and 1 tablespoon smoked Spanish paprika. Roast for 2 hours or until the internal temperature reaches 175°F (79°C).

Remove the pork from the oven and let it cool for about 15 minutes. Shred the pork using two forks, discarding any large pieces of fat.

Preheat a griddle or panini press over medium heat. Slice the hoagie rolls in half and spread mayonnaise on both sides. Layer the sandwich with domestic ham, shredded pork, dill pickle chips, and Swiss cheese. Spread a layer of brown mustard on the top half.

Butter the outside of each assembled sandwich with unsalted butter. Grill for about 3-4 minutes on each side, or until the rolls are golden brown and the cheese has melted.