That is no accident.

"Our regulatory model is copied from that of Champagne," she says later, to ensure that every bottle is properly region-specific and of the labeled quality. Her agency has registered 1,360 brands in her home country, and individual blue agave plants are literally tracked from birth. "Every blue agave in the system gets a serial number at the time of planting," she says, noting that her agency monitors planting, harvesting, distilling and bottling.

Raising the glass in her hand, she adds: "We know precisely where the agave in the tequila we are drinking here came from."

The Mexican agency she works for is just 20 years old - "we turn 21 this year, so we can drink and drive," she jokes - which means it started with modern tools and measures to track the ancient craft of agave-distilling.

In China, where "fake" liquor is a perpetual cloud over cocktail bars, tequila lovers can feel relatively secure that their premium brands are the real thing, because it's so new in the market. In other developing countries - and even in Mexico - there is plenty of phony "tequila" made in underground laboratories and even bathtubs.

"But my friends in the cognac and whiskey industries here have been warning me: It will come," she says.

At a glance

There are five classes of tequila. In order of increasing color (and cost):

* White (silver) is bottled straight from the second distillation. It's clear as water, having no color.

* Yellow (gold) is also a fairly "young" tequila, a mix of white and aged tequila that has a pale yellow color.

* Aged (reposado in Spanish) is aged for about two months, faintly golden in color thanks to the barrel wood. It has a faint vanilla scent and a softness in the mouth-feel.

* Extra-aged (anejo) has been barrel-aged for at least one year and for as long as three. The smell is sweet, with notes of butterscotch or caramel.

* Extra-anejo must be three years in the barrel and can be aged for up to 25.