Slice the potatoes into ½-inch (1cm) slices, then cut the slices into ½-inch (1cm) strips.
Place the sliced potatoes on a baking sheet along with the pork shoulder. Make sure that the potatoes are not touching the pork.
Drizzle the olive oil over the potatoes, then sprinkle the pork and the potatoes with the salt and pepper, rubbing them in so that they are all coated evenly. Cover the pork with one cup (286g) of the barbecue sauce, then rub it evenly on all sides. Bake for 45 minutes.
Remove the fries, then place the pork in the center of the tray. Bake for another two hours at 350°F (175°C)
Transfer the pork to a large bowl, and using two forks, shred the pork. Combine the pulled pork with the remaining one cup (286g) of barbecue sauce.
In a skillet or a baking tray, layer half of the fries, half of the bbq pork, half of the red onion, the pepper jack, half of the scallions, then repeat with the remaining fries, pork, red onion, cheddar, and scallions. Bake for 15 minutes, until cheese is melted.