Cook sweet potato in boiling salted water until tender; drain, peel, and cut in half lengthwise or slice. Peel apples and slice. Layer sweet potatoe and apples in 2 qt baking dish. Sprinkle lightly with salt.
In medium saucepan mix brown sugar, cornstarch and salt; blend in orange juice. Cook over high heat, stirring constantly, until mixture comes to a boil. Add butter, sherry, walnuts, and orange peel; pour over potatoes and apples. Bake uncovered in a preheated 350 degree F oven for 20 to 30 minutes or until well glazed.