Cover prunes with the brandy in a small sauce pot and bring to a simmer. Remove from heat and set aside for at least 1 hour, although refrigerated overnight is better.
Preheat oven to 350° F. Stand the potatoes on end and arrange them as closely as possible in a 14-inch straight-sided braising pan, or other large, deep covered pan. Add enough fresh cider to cover just to the tops of the potatoes. Add cloves, bay leaves, thyme and salt.
Cook potatoes uncovered, basting every 10-15 minutes, for 45 minutes, or until tender when pierced with a fork. Transfer the pan to the stovetop over low heat and simmer until the cider has reduced to a light syrup. If desired, finish by topping the dish with butter or hazelnut oil. Top with the prunes, chopped hazelnuts and apple slices before serving.
Serves 6 to 8