Boil potatoes. With a sharp knife peel warm potatoes and cut into 1/3-inch-thick slices. In a bowl immediately toss potatoes with vinegar. In a bowl mash yolks and stir in mayonnaise, mustard, and onion. Chop whites and celery and gently toss together with potatoes, mayonnaise mixture, and salt and pepper to taste. Serve potato salad chilled or at room temperature Serves 6. Suggested additions: dill pickle, fresh chives, poppy seeds, crab meat, or corn. Recipe by: From Gourmet Magazine, July 1997 Posted to MC-Recipe Digest V1 #748 by C4 on Aug 19, 1997