Pat the pork collar dry and season all over with Salt Pepper + Three Chiles seasoning . You can dry brine this overnight, uncovered in the fridge or tightly wrapped in plastic – just remember to turn your wrapped collar about halfway through brining.
Remove the pork collar from the fridge. Set a smoker to low heat about 250 degrees F. Add the collar directly to the smoker and cook low and low until it hits an internal temperature close to 200 ° F, this will take 4 to 5 hours. Remove the collar from the smoker, cool it for 10 minutes and wrap tightly in butcher paper to rest for an hour while you prep the potatoes.
Heat the grill or oven to 400 degrees F. Coat the potatoes with olive and season on all sides with kosher salt. Roast for about 40 minutes or until fork tender. Remove from the grill and cool.
When the potatoes are cool enough to handle, cut them in half lengthwise, scoop out the tender potato insides (leave about ⅛ inch potato in the skins for structure) and add this to a large mixing bowl. Add the sour cream, half of the cheddar cheese, parmesan, butter, and half of the scallions. Season with a heavy pinch of salt. Add the buttermilk. Use a potato masher to mix and smooth this filling. Scoop ½ cup of the mixture back into each of the potatoes and arrange on a rimmed baking sheet. Top each potato with some of the remaining cheddar cheese.
Return to the grill or smoker. Cook the potatoes until they are warmed through and the cheese is melted and browned, about 15 minutes. While the potatoes cool, shred the pork and toss it with the BBQ sauce.
Pile pork on top of finished potatoes top with scallions, a dollop of sour cream and drizzle of olive oil.