Old World yams and New World sweet potatoes are indeed different vegetables. In the US today, the terms are often used interchangeably to describe popular varieties of red-skinned, orange-fleshed tubers with pointed ends. At Earthbound Farm we produce the Garnet and Jewel varieties, which are commonly called yams but are actually sweet potatoes. No matter what you call them, though, they're delicious!
Roasting yams brings out their sweetness and keeps them moist and tender. Here we've added cubes of sweet-tart quince to the mixture, which makes for a beautifully balanced pairing. Quinces are typically in season from October through January; if they're not available near you, substitute tart apples such as Granny Smith or Fuji.
Position a rack in the lower third of the oven and preheat to 450 degrees F.
Place the yams and quince in a large bowl. Add 4 tablespoons of the maple syrup and the olive oil, tossing to coat the mixture evenly. Sprinkle with the salt and thyme, add pepper to taste, then toss again.
Spread the mixture into a single layer on a rimmed baking tray, adding any juices that have accumulated in the bowl. Bake until the yams and quince are tender and slightly caramelized, 40 to 45 minutes.
Transfer the mixture to a platter. Drizzle with the remaining maple syrup and sprinkle with the sage. Serve hot.