Using a sharp knife cut a deep slit through the side of each pork chop toward the bone to make a pocket.
Brown the sausage over medium heat in a frying pan; break up the sausage with a wooden spoon. When cooked through, drain and transfer to a large mixing bowl. Return the frying pan to the stovetop and melt the butter.
Saut the onion and celery for 3 to 5 minutes. Add the garlic and saut for another minute. Add to the bowl with the sausage along with the breadcrumbs, and parsley.
In a separate bowl, whisk together the egg and 1/2 cup chicken broth. Stir in the cheese and season with salt and pepper. Pour over the sausage and breadcrumb mixture and toss gently with a rubber spatula. If the mixture seems dry, add more chicken broth as needed. (Do not over-moisten; the mixture should not be soggy.)
Open the pockets of the pork chops by pressing on the sides; generously stuff each chop with the stuffing mixture. If desired, pin the pockets closed with toothpicks.
When ready to cook, start the Traeger grill on Smoke with the lid open until the fire is established (4 - 5 minutes). Set the temperature to 350F and preheat, lid closed, for 10 to 15 minutes.
Arrange the chops directly on the grill grate and grill, turning once, for 35 to 40 minutes, or until done to your liking. (The temperature of the meat should be at least 140F when read on an instant-read meat thermometer; the temperature will rise about 5 as it rests.)
Let the chops rest for 5 minutes, then transfer to a platter or plates. Remove any toothpicks before serving. Enjoy!