The Lentille Verte du Puy is one of France's most prestigious agricultural products, grown on the volcanic plateau around Le Puy and protected by an AOC (Appellation d'Origine Contrôlée) designation since 1996. The lentils are small, dark green with grey-blue marbling, and have a distinctive earthy, slightly peppery flavour that holds its shape well after cooking — characteristics attributed to the volcanic basalt soil and the altitude of the plateau.
Every restaurant in Le Puy serves them in some form. The classic preparation is a warm lentil salad with vinaigrette and lardons, often paired with sausage from the Auvergne. Look for the AOC label to confirm you are eating the genuine article from the Velay plateau rather than ordinary lentils. The local market is a good place to buy lentils to take home; the vendors are usually happy to explain how to cook them.