Although sweet potatoes are often called yams, these two vegetables aren't related. Sweet potatoes are a tropical root that belong to the morning glory family; yams are a tropical vine tuber. Yams are moister and sweeter than sweet potatoes, but they are not generally available in American markets.
Sweet potatoes come in two varieties. One has a thin yellow skin and dry pale flesh; the other has a thick, dark-orange or pink skin and moist, bright-orange flesh. Dark sweet potatoes will be the sweetest.
Arrange the pork chops, sweet potatoes and apples on a pretty serving platter and drizzle it with the pan gravy. Garnish with sprigs of fresh thyme, chopped green onions, or green onion "fans."