On rack in broiling pan, broil pork chops, turning once, until rare. Preheat oven to 325º. Arrange chops in casserole that is large enough to hold them in 1 layer and sprinkle with 1/8 teaspoon each salt, pepper and thyme. Add broth, cover casserole and bake for about 45 minutes.
While pork chops are baking, heat margarine in small skillet until bubbly and hot. Add onion and garlic and sauté until onion is translucent. Add mushrooms, celery and remaining 1/8 teaspoon each salt, pepper and thyme. Sauté for 5 minutes. Stir in bread cubes. Spoon an equal amount of stuffing mixture on to each baked pork chop. Bake uncovered for 15 minutes longer.