Adapted from A New Way to Cook by Sally Schneider and found at splendidtable.com. If you don't have Armagnac, any good brandy may be used. The prunes are sublime served over vanilla and coffee ice cream and as an ingredient in pear, apple, or quince tarts. Prepare at least 1 week before serving to allow the prunes to mellow. Since they last indefinitely, you can keep them on hand for instant desserts. Packed in a pretty jar, they make a welcome gift. There is a 1 week standing time.