N'gaan is a type of plant-derived spice that is used as a flavoring in food and beverages. Although many native Vulcans insist that it is a distinctly flavored product, the Human senses of smell and taste register n'gaan as being a close match to peppermint. One popular use for n'gaan is in the creation of a type of milkshake that is popular among Vulcans.
Spock and T'Vau once had an occasion to meet each other and share n'gaan shakes, an occasion that Spock apparently did not relish the memory of. T'Vau became a quite regular drinker of n'gaan shakes, as noted by her crewmates aboard the USS Jefferson Randolph Smith. The Jefferson Randolph Smith ship's computer noted the frequent order and made the shakes a default food choice in situations where food was being requested. Captain Tatyana Trofimov accidentally initiated an unintentional food synthesizer request which caused a shake to be dispensed as the crew was entering an escape pod. When the ship's computer disengaged control of the pod, a program error caused the pod computer to not resume control of the food synthesis process. Without the original computer's shutoff order, the food slot on the escape pod continued to dispense shake until the pod's supply of raw materials for food synthesis was expended. Upon landing, the crew barely managed to exit the pod in time to prevent their drowning in the milkshake. (TOS - Worlds Apart novel: How Much for Just the Planet?)