Defrutum is made by boiling down grape juice (called must) in large kettles until it had been reduced by at least half. The sweetest defrutum was further boiled down into an even stronger concentrate called sapa. This is a thick fig syrup. It is used in Pullum Frontonianum, a dish from ancient Rome, found in Apicius, a cookbook from ancient Rome from the 4th or early 5th century, which allegedly written by Marcus Gavius Apicius. This is how to make defrutum: