Freeze the cabbage overnight (this will wilt the leaves); thaw before using. Remove the core with a paring knife and carefully peel the leaves apart without tearing. Discard the outermost, dark green leaves; they are not as tender as the paler leaves. You'll need 10 to 12 leaves. (Reserve the remaining cabbage for another use.)
With your knife nearly parallel to the cutting board, carefully shave off the thick center vein working toward the bottom of each leaf. Set the leaves aside.
Meanwhile, in a large mixing bowl, combine the beef, pork, rice, onion, garlic, parsley, egg, and Traeger Cajun Rub and mix well. In another bowl, combine the crushed tomatoes and tomato soup and season to taste with salt and pepper.
Lay a leaf on your work surface. Form a portion of the meat mixture into a sausage-like log about 1-1/4 inches thick and 2-1/2 inches long and place it near the bottom of the leaf (where you trimmed the vein). Fold the two sides over the ends of the log, then roll up from the bottom. Arrange in a single layer in a baking dish, seam-side down. Repeat until you run out of meat. Pour the tomato sauce mixture over and around the cabbage rolls and cover tightly with foil.
When ready to cook, start the Traeger grill on Smoke with the lid open until the fire is established (4 to 5 minutes). Set the temperature to 350F and preheat, lid closed, for 10 to 15 minutes.
Bake the cabbage rolls for about 1 hour, or until the internal temperature of the meat mixture is 160. Serve with sour cream and chives, if desired