In Philadelphia the roast pork Italian is the sandwich that locals will tell you to order instead of the cheesesteak, and the reason is the broccoli rabe. This is a pork sandwich built around a bitter green: pork shoulder roasted long and slow with garlic, rosemary, and fennel until it shreds, sliced thin, and piled on a long Italian roll with sharp provolone and a tangle of garlicky, faintly bitter rabe. The rabe is not a vegetable on the side. It is the structural counterweight that keeps a rich, fatty, deeply seasoned pork from collapsing into one heavy note, and the sharp provolone, aged and aggressive rather than mild, is chosen to push back just as hard. Without those two the sandwich is a pork roll. With them it is its own thing.
The craft is in the roast and the assembly. The shoulder is cooked until the connective tissue gives way and the meat pulls into tender, jus-soaked strands, then sliced or chopped so it stays pliable in the pile rather than seizing into rope. The pan juices are saved, because a good build dips the cut faces of the roll or spoons the jus over the meat so the bread carries the pork's seasoning through every bite. The broccoli rabe is blanched to take the rawest edge off, then sautéed hard in garlic and oil so it stays bitter and structural instead of going to mush. The sharp provolone is laid against the hot meat so it half melts and binds the pile. The roll has to be the Philadelphia long roll: a tender interior and a crust with enough spine to hold a heavy, wet, three-part filling without folding at the middle. Built right it is hot, sharp, bitter, and fatty in one bite, assembled fast at a counter and eaten before the jus has time to win.
The variations are mostly swaps of the green and the heat. Trading broccoli rabe for sautéed spinach makes a milder, sweeter sandwich. Adding fried long hot peppers turns the heat up and the bitterness sideways. Both of those deserve their own articles rather than being crowded in here, as does the cheesesteak that this sandwich is forever measured against and the Schmitter that runs a different logic on the same roll.