* In a large saute pan, melt the butter and oil over moderate heat. Add the onions, celery, and pepper and cook until the onions are wilted, about 5 minutes, stirring frequently.
* Add the thyme and ham and cook, stirring for 2 more minutes. Add the bread cubes and mix thoroughly. Stir in the chicken stock and remove from the heat. When cool, mix in the cheese, egg,and seasonings and stir to combine well.
* Lay the pork loin cut side up and vertical, season with salt and pepper. Place the stuffing in a vertical row in the center of the loin. Wrap the meat around the filling and secure with the butcher's string. Season the exterior with additional salt and pepper.
* Roast on a roasting rack in a preheated 350°F oven for 1 hour, or until a meat thermometer inserted in the center of the loin reads 145°F.
* Remove from the oven and let stand for 15minutes. Remove strings, then slice and serve.