Apply a thin coat of yellow mustard to the surface of the chuck roast.
Coat the chuck roast with bbq rub. Place the chuck roast in a cast-iron skillet.
Set up your smoker to smoke at 275 degrees using indirect heat.
Smoke the chuck roast for 2 hours, and then flip in the cast iron skillet.
Continue cooking until the internal temperature hits 160 degrees, and then cover tightly with foil. When the internal temperature hits 200 degrees remove the cast iron skillet from the smoker and place in a large cooler to rest.
While the chuck roast is resting peel the butternut squash, scoop out the seeds, and cube it.
Coat in olive oil and toss in salt, pepper, and brown sugar.
Arrange the cubes on a lined baking sheet and cook in your smoker at 375 degrees for 25 minutes.