Place the chuck roast on a plate, then pat dry with a paper towel.
Coat the roast with mustard, set aside.
In a small mixing bowl, mix together the dry rub ingredients, salt, ground pepper, garlic powder, onion powder, celery seeds, and paprika.
Sprinkle the rub over the roast and pat down into the roast to fully coat. Be sure to cover all sides.
Place in a plate or tray, it's best to wrap in an airtight container. This can be done with a 9x13 pan, wrapped with foil or plastic wrap.
Let it rest in the fridge overnight or at least 12 hours.
Day of Cooking:
Prepare for 8+ hours of cooking time.
Bring the grill to 250*F, this can be done with a charcoal smoker or a pellet grill.
Once the temperature has been reached, place the chuck roast on the grill, close the cover and let it cook until it reaches about 150-160*F. This normally takes about 4 hours, but it's best to check the temperature throughout the cooking time.
Once the temperature is reached, cut aluminum foil to wrap around the roast.
Place the roast on top of the foil, then brush it with bbq sauce (pour about 1/4 cup of the bbq sauce into a small dish and brush with this, then discard) Add the diced butter right on top.
Wrap up the chuck roast tightly then place it back on the grill/smoker.
Continue to cook now until the internal temperature reaches at least 190-205*F.
Once this temperature has been reached, carefully remove and let it rest on a cutting board for about 30 minutes.
While the meat is resting, increase the temperature of the smoker or grill to 350*F.
Unwrap the roast carefully and dispose or any liquid in the foil. Cut it into bite size pieces about 3/4inch cubes.
Place it in an aluminum pan.
Pour the remaining bbq sauce on and sprinkle with brown sugar.
Very carefully mix this in, the meat will be tender so mix carefully.
Once the smoker or grill has reached 350*F, place the foil pan back on the grill.
Cook for an additional 30-40 minutes.
Remove and Serve.
Notes
If you prefer homemade sauce, check out this homemade barbecue sauce.A meat thermometer is an absolute MUST for this recipe, it will be needed to check the internal temperature throughout the cooking time.This can be made in a Big Green Egg or Pellet Grill.