If your pork is already tied up, leave it that way. Rub it all over with the seasoning rub you made. Cover or wrap in plastic and allow it to sit in your fridge 8-24 hours.
When ready to roast the pork. Allow it to sit on your counter for 30 minutes. Preheat oven to 450 degrees.
Place pork in a casserole dish or oven pan with 1 inch or greater sides, add 1 ½ cups water and 5 cloves garlic and cook for 15 minutes then lower oven temperature to 300 degrees and continue cooking until internal temperature of the meat is 140 degrees F. (about 1 ½-2 hours depending on the size of your pork.
Remove pork from the oven and allow it to cool completely. Cut off any twine/strings/elastic.
Wrap it in foil and place it in the fridge overnight.
Slice it thinly 8-24 hours later (as thin as you can get it). You want the meat completely chilled before you slice it so all juices stay in the meat.
Bring a large pot of salted water to a boil.
Prepare an ice bath (a bowl of cold water with a couple handfuls of ice). Once water is at a rolling boil, cook broccoli rabe for 1 minute, strain broccoli rabe from the boiling water (or use a slotted strainer to remove) and immediately place into ice water bath.
Remove broccoli rabe from the ice bath and blot with paper towels till dry (this can be done ahead of time as well).
SAVE all pork liquid from your pan in a jar or container for your jus, add a little water if necessary to scrape up any bits and pieces.
When ready to saute the broccoli rabe, coat a saute pan with grapeseed or olive oil, add in 5 cloves of smashed garlic and a couple pinches of red pepper flakes. Allow the garlic to turn golden and then discard it.
Add in broccoli rabe, toss it with the oil to coat, season well with salt and pepper and cook until heated through (2 minutes).
Chop it up into bite sized pieces and set it aside on a plate until ready to use in sandwich assembly.
Heat pork juices saved from previous day with the 2 cups of vegetable stock (if you wish for extra flavor toss in a couple cloves or smashed garlic and red pepper flakes as it heats, if you have a sprig of Rosemary or Thyme, add that in too however it is not necessary.
Bring liquid to a boil and then turn off the burner.
Toss the broccoli rabe into the liquid just to heat it through and remove.
Add in as much of the sliced pork as you may be using for however many sandwiches you are making at the time.
If toasting your rolls, preheat oven to 350 degrees, cut open rolls and place 3-4 slices on each roll, overlapping them some. Place on baking sheet and bak just until rolls crist up and cheese begins to melt.
If not toasting your rolls, cut open rolls and place 3-4 slices on each roll, overlapping them some (the heat of the meat will slightly melt the cheese which is what you want)
Add your meat onto the rolls followed by the broccoli rabe, season with a little salt & pepper and spoon a small amount of the au jus overtop and dig in!
Tip: If your pork roast has a layer of fat, score it with the tip of a sharp knife in a criss-cross pattern and place the fat side down when cooking. This helps flavor the drippings and eventually the au jus.