Split and toast the hoagie rolls in a preheated oven or toaster oven until slightly dried out and lightly toasted.
Lay open the hoagie rolls on a clean work surface; spread 1 tsp. butter on one side of each roll and ½ tbsp. mustard on the other side. Top each roll with even amounts of ham, pork, and cheese; add pickles and close sandwiches.
Spread the remaining butter (2 tbsp.) on the outside of each sandwich (top and bottom) and wrap in aluminum foil. Press down on sandwiches to flatten slightly.
Heat a grill pan over medium-high heat.
Place foil-wrapped sandwiches in preheated grill pan, as many as will fit. Place another heavy skillet on top of sandwiches to apply constant pressure. Cook sandwiches 3-4 minutes per side. Remove sandwiches from heat and discard foil. If necessary, return sandwiches to pan and cook another 2-3 minutes or until sandwiches are heated through and bread is crispy and golden brown. Repeat with remaining sandwiches.
Transfer sandwiches to a cutting board and cut at an angle into halves. Serve immediately.