Charleston Sweet-Potato Pancake

In cup, mix cornstarch, thyme, salt, and pepper. In large bowl, toss sweet potatoes and apples with cornstarch mixture. Then, toss with 3 tablespoons melted margarine or butter. Heat nonstick 10-inch skillet until very hot over medium heat. Add remaining 1 tablespoon margarine or butter. When melted, spoon potato mixture into skillet; pat to an even thickness. Cook, covered, 18 to 20 minutes, until potatoes and apples are tender. Uncover skillet; cook 2 minutes longer. Remove skillet from heat. Place large serving plate over top of skillet. Quickly turn skillet upside down to invert pancake. Replace any pieces on top of pancake that may have stuck to skillet. Garnish with thyme sprigs if you like.