This is a classic method of transforming prunes into a fabulous, if somewhat alcoholic, fruit preserve. Traditionally, ordinary dried prunes were used. Once the preserve is ready to eat, it may be served with a wide variety of desserts or on its own as a simple end-of-meal treat.
Pack stoned, ready-to-eat prunes in a large preserving jar and cover with Armagnac or another brandy. Ensure that there are no air bubbles in the jar, seal it tightly and leave for at least a month. Store for up to one year.