Heat in a large skillet:
      2 tablespoons butter
      1 tablespoon vegetable oil
Add and toss together:
      1 1/2 pounds sweet potatoes or yams, peeled and cut into 1/4 -inch-thick rounds
      3 red apples, cored and cut into rounds
      1/3 cup packed light brown sugar or dark brown sugar
      1/2 teaspoon salt
Add:
      1/4 cup apple juice or water
Cover and cook over low heat until the sweet potatoes are tender, about 30 minutes. Uncover, increase the heat to medium, and cook about 5 minutes more, turning the potatoes and apples every so often so that they are well caramelized but not burned. The juices should boil away. When done, season with:
      Ground black pepper to taste