Preheat your Yoder Smokers YS640 pellet grill to 250ºF. Rub the chuck roast with a binder (oil, mustard, beef stock concentrate). Just a thin layer to allow the rub to attach. Season all surfaces with Cattleman’s Grill California Tri-tip Seasoning. Smoke for about 2.5 hours, or 155ºF internal temperature. Remove from the grill, wrap tightly in foil and return to the grill. Turn the grill up to 325ºF. Continue cooking until the internal temperature reaches 205ºF-210ºF, and is tender enough to shred. Increase the grill temperature to 425ºF, and place a Lodge Logic 12” cast iron skillet inside to preheat.
Add a little oil to the skillet. Add the leeks and carrots to the skillet. Cook until carrots begin to soften and leeks become translucent, about 10 minutes. Add the garlic, tomato paste and 1-2 tablespoons Cattleman’s Grill California Tri-tip Seasoning. Cook for about 2 minutes. Add the frozen peas and remove from the grill. Remove the veggies from the skillet and set aside.
Combine the cooked potatoes, milk, butter and parmesan. Whip into mashed potatoes. Adjust seasoning and consistency as necessary.
Shred the chuck roast and add it to the skillet. Place the veggies on top of the shredded roast. Spread the mashed potatoes over the veggies. Top with the cheddar cheese. Place in the grill until the filling is hot and cheese is melted, about 20-30 minutes. You may brown the top with a torch to finish, if desired.