The result was nice - a less citrusy sidecar. The citrus flavors still dominate, though. It's not the best drink for appreciating the Armagnac itself. The prune, however, is good for that.
Evidently both prunes and Armagnac are popular in Gascony, thus the name of the drink. As such, my wife said "All for one an one for all" as part of our toast. I will confess, I didn't know The Three Musketeers were from Gascony.