If using a panini press or griddle, heat it to a medium to medium high heat.
Slice the bread lengthwise and spread both sides with mustard. Lay half of the cheese on the bottom slice of bread. Top with pickles, followed by ham and roast pork. Top with the other slice of bread and brush with melted butter.
Place the sandwich in the panini press (Note: if sandwich is too large, carefully cut it in half or quarters and cook in two or three batches.)
If cooking on a griddle, place the buttered side of the bread down on the griddle. Lay a piece of parchment paper over the sandwich and use a heavy cast iron skillet or other heavy pan to press the sandwich. Cook until cheese gets melty, then flip sandwich and continue cooking until the other side of the cheese melts and the sandwich is hot and crispy on the outside.