This intensely-flavoured green herbal liqueur has been distilled in the French mountains near Grenoble by the monks of Grande Chartreuse monastery, based on an alchemical recipe for an "elixir of long life" going back to 1605.
As a drink it's delicious on its own, makes a rich and warming addition to hot chocolate, and is well-known as an ingredient in the Last Word cocktail. Mowgli Street Food use it in one of their house cocktails, too.