Among the different varieties of chestnut is one that contains three individually partitioned kernels (châtaigne), small and somewhat triangular in shape.  These varieties should not be confused with "horse chestnuts," (Aesculus hippocastanum), which are not edible but whose seeds are used in pharmaceutical products.
 

However, the preferred kind for sweet-making (marron) has a single kernel, bigger, plumper and more flavourful, that keeps longer and holds up better during cooking.