A good Cognac is subjected to a complex manufacturing process. It is never made from the eau-de-vie of a single cru, but from a `marriage' of eaux-de-vie that vary in age and cru - some as old as a hundred. To establish the age of a Cognac, only the number of years spent in oak casks or barrels are taken into account. As soon as an eau-de-vie is decanted into a glass recipient, it ceases to age. The longer it is left to age, the more a Cognac gains in complexity, fragrance, aromas and taste (spiced, pepper and cinnamon flavours).