1. Preheat oven to 350 degrees F. Place roast, bone tips up, on a rack in a shallow roasting pan. Cover ends of bones with a strip of foil. Bake for 1 1/2 hours.
2. Lightly grease an 8 x 8 x 2 in. deep baking dish; set aside.
3. Melt butter in a large skillet over medium heat; add sausage and onion. Cook until onions are tender and sausage is cooked through, about 12 minutes.
4. Remove pan from heat, add bread cubes, broth, 2/3 cup chestnuts, parsley, sage and thyme. Season with salt and pepper. Toss to combine.
5. Fill roast cavity with stuffing mixture. Place remaining stuffing in the baking dish. Cover stuffing in cavity and in baking dish with foil. Continue roasting roast and stuffing for 30 minutes or until meat thermometer registers 150?F (Allow 20 minutes per pound total roasting time). Brush occasionally with pan juices.
6. Carefully transfer roast to serving platter. Garnish with remaining chestnuts, fresh herbs. Carve pork between bones into chops to serve.