Marron glacé that a "marron glacé" is a confit marron that is covered in caramel. The 1767 book "L'agronome, ou dictionnaire portatif du cultivateur" claimed that the best marrons came from the Dauphiné region in southeastern France, and contained instructions for preparing marron glacés. Chestnuts are covered with a membrane, known as a pellicle or episperm, which closely adheres to the fruit's flesh and must be removed because of its astringency. Marron nuts have a pellicle which is "superficially attached to the nut", making it easily removable from the fruit. Some chestnuts have two cotyledons usually separated with deep grooves penetrating nearly
Marron glacé all the way through the fruit; this makes them too fragile for the necessary manipulations during the cooking process. There also are other grooves on the surface, which means more embedded pellicle that must be painstakingly removed. "Marron"-quality nuts do not have the separation into two cotyledons; it appears in one piece and it shows few very shallow grooves. In Italy, the term "marron" denotes a specific high-quality cultivar of "Castanea sativa" bearing oblong fruits with a shiny, reddish epicarp and often exhibiting a small rectangular hilar scar. As with the French use of the term, there should be no