A vol-au-vent is a small hollow case of puff pastry. It was formerly also called a patty case.
A vol-au-vent is typically made by cutting two circles in rolled out puff pastry, cutting a hole in one of them, then stacking the ring-shaped piece on top of the disc-shaped piece. The pastry is cooked, then filled with any of a variety of savory or sweet fillings.
The pastry is sometimes credited to Antonin Carême. However, an entremet called petits gâteaux vole au vent is mentioned in François Marin's 1739 cookbook Les Dons de Comus, years before Carême's birth.