By Harold McGee
True balsamic vinegar, aceto balsamico, is a vinegar like no other: almost black in color, syrupy, sweet, remarkably complex in flavor, and remarkably expensive, all thanks to decades-long fermentation, aging, and concentration in wood casks. It has been made in the northern Italian state of Emilia-Romagna since medieval times. Individual households produced their own as a kind of general-purpose, soothing tonic, or balsam. It wasn’t until the 1980s that the rest of the world discovered balsamic vinegar, a discovery that fostered the development of less elaborate and less costly approximations. The label term tradizionale, “traditional,” is reserved for the original version.