Season the shoulder roast with salt and pepper and refrigerate for several hours or overnight.

Preheat the oven to 400°F. Coarsely chop the tomatoes, onion, carrot, and celery, and put them in an earthenware baking dish or roasting pan just large enough to hold the meat. Add the chicken stock, white wine, garlic, thyme, peppercorns, and chili pepper. Add the seasoned lamb shoulder and roast for 1 hour, checking the level of liquid every once in a while and adding more stock or water if it gets too low. Turn the roast and cook for 30 minutes more. Turn again and roast for 20 more minutes, until golden and crisp. The meat should be soft and tender, and almost falling off the bones. Carefully remove the meat and cool at room temperature. When the shoulder is cool, gently remove the bones and cut the meat into thick slices.

To make a simple sauce, pass the braising liquid and vegetables through the coarsest disk of a food mill. Allow the sauce to settle and thoroughly skim the fat. Taste for seasoning. Thin with a little stock, if necessary, or reduce over medium heat to thicken. You may roast the shoulder and prepare the sauce several hours before serving.

Season the chops with salt and pepper and grill over medium coals just past medium-rare, about 3 minutes per side. At the same time, grill the pieces of shoulder until warm and crisp. Arrange the meat on a platter, and spoon some of the warmed sauce over it.