Sherried Sweet Potatoes and Apples

In a kettle combine the sweet potatoes with enough cold water to cover them by 1 inch and boil them for 35 minutes, or until they are just tender. Drain the sweet potatoes and let them cool until they can be handled. The sweet potatoes may be prepared in advance up to this point and kept chilled overnight. Peel the sweet potatoes, cut them lengthwise into sixths, and cut the lengths crosswise into 1/2-inch pieces. Peel, core, and cut the apples lengthwise into sixths and cut the wedges crosswise into 1/2-inch pieces. In a large heavy skillet cook the apples in the butter over moderate heat, stirring, for 3 minutes, or until they are softened. Stir in the lemon juice, the brown sugar, the cinnamon, and the Sherry, bring the liquid to a boil, and simmer the apples for 3 minutes. Add the sweet potatoes and cook the mixture, stirring gently and trying not to break up the sweet potatoes, for 2 minutes, until it is combined well and heated through. Transfer the mixture to a heated serving dish.