Marinate the pork loin chops for 30 minutes with a little olive oil, the garlic, rosemary and a grinding of pepper.
Meanwhile place the onion wedges in a roasting dish and sprinkle a little olive oil and balsamic vinegar over them. Season generously with salt and pepper.
Cover dish with foil and roast at 180ºC for 20 minutes, then remove the foil.
Place the pork chops on a rack over a roasting dish, and cook them beside the uncovered onions for 12 – 15 minutes until cooked through.
Serve with watercress salad and a little more balsamic vinegar sprinkled on the onion