Preheat your Z Grills pellet smoker to 225ºF.
In a bowl,combinethe dry ingredients including½ cup of brown sugar,paprika, pepper, garlic, minced onion, and chili powder.
Coat all sides of the pork butt with olive oil, then sprinkle with salt evenly on all sides.
Apply the prepared spice mixture and rubto the pork butt, ensuring to get the rub onto all sides and the crevices.
Place the pork butt on the grilling grate and smoke for about 6 hours, or until a meat thermometer inserted into the thickest portion registers 165ºF.
Remove the pork from the smoker to analuminum roasting pan. Sprinkle it with the remaining brown sugar and place the stick of butter on the top of the pork. Cover the pan with tin foil and transfer it back into the grilling grate.
Continue cooking the pork, for about 4-6 hours. Until it reaches an internal temperature of 203ºF.
Remove the pork from the smoker and let it rest for 2 hours before unwrapping.
Pull apart and enjoy.