Lay your pork butt down with the fat cap facing upward and pat the entire roast dry.
Score the fat cap in a crosshatch pattern with a sharp knife.
Use the mustard to coat the entire roast - this will act as a binder to help your seasoning stick to the meat.
Season the pork butt liberally on all sides with the BBQ rub.
Let the pork sit at room temperature while you preheat your pellet grill to 225°F.
Place the pork butt directly on the grates of the smoker with the fat cap facing down.
Smoke for 16-18 hours, or until the internal temperature reaches 200°F and the pork butt is probe-tender.
Remove from the smoker and let rest for 30 minutes, then shred and serve immediately.
