Rub oil on some unpeeled, uncut sweet potatoes and bake them for an hour or more until a fork goes through them easily. Shortly before they’re done, put a covered pot of cranberries with a little water over medium heat; after boiling for a few minutes, the berries will all burst. Turn off the flame and add enough maple syrup to the berries so that they’re no longer bitter. When the potatoes are done, chop them roughly and add butter, salt, and pepper; then spoon some or all of the cranberry sauce over them and add some walnuts. Mix well and serve hot.