Somebody at the table pours it into a shot glass, throws it back, and winces. That is the single most common thing that happens to a good bottle of mezcal, and it is a small tragedy every time. Mezcal is not tequila's rowdy cousin, to be dispatched in one gulp. It is a slower, smokier, more thoughtful drink, and once autumn arrives it makes far more sense than almost anything else on the shelf.

The confusion is understandable. Both come from the agave plant, both are Mexican, both live in the same corner of the drinks cabinet. But calling mezcal smoky tequila is a bit like calling Champagne fizzy wine. Technically in the right postcode. Miles off the point.

It all starts with the agave

Here is the cleanest way to hold the difference in your head. Tequila can only be made from one plant: blue Weber agave. That is the rule, full stop. Mezcal, by contrast, can be made from dozens of different agave species, from the hard-working espadin to wild, high-altitude varieties that take a decade or more to mature. Tequila is a soloist. Mezcal is the whole orchestra.

Geography draws the other line. Tequila comes mostly from the state of Jalisco, with a handful of permitted municipalities elsewhere, and its heartland is the town that lent the spirit its name. Mezcal's spiritual home is Oaxaca, in the mountainous south, though its protected zone now reaches across several states. Both are guarded by a Denominacion de Origen, the Mexican equivalent of the rules that stop a sparkling wine from Kent calling itself Champagne.

Where the smoke comes from

If tequila and mezcal taste different, and they really do, the reason is fire. Most tequila is made by steaming the agave hearts, the pinas, in ovens or industrial autoclaves. Clean, efficient, no smoke. Mezcal takes the older road: the pinas are roasted in conical pits dug into the earth, lined with volcanic rock, and packed over burning wood for days. That underground barbecue is where the smoke comes from.

And it is not always a bonfire. A young joven, bottled unaged and fresh, can wear its smoke like a whisper rather than a shout. Ilegal Joven is exactly that: floral and gently sweet, with the smoke sitting politely in the background. It is the bottle to hand a sceptic.

A drink that refuses to be rushed

Part of mezcal's appeal is how gloriously inefficient it is. A single palenque, or village distillery, might turn out only a few hundred bottles a year, made by a family who have been doing it for generations, often with no additives and no shortcuts. The wild agaves are foraged, not farmed. The stills are small copper pots. Nothing about it scales the way industrial tequila does, and that is precisely the point.

Which is why mezcal has quietly become the connoisseur's agave spirit. Bartenders champion it, drinkers who cut their teeth on tequila trade up to it, and its smoky, savoury character suits the darker half of the year far better than a poolside margarita. It rewards the person who slows down. In an autumn of early sunsets and long dinners, that is no small thing.

How to drink it, and how not to

Forget the salt, forget the lime wedge clenched between the teeth, and above all forget the shot. In Oaxaca they say you should kiss mezcal, not gulp it. Pour a little into a copita, a small clay cup, or a plain wine glass, at room temperature, and take it in slow sips. The traditional companion is a slice of orange dusted with sal de gusano, a smoky, savoury worm salt, though a good bottle needs no accessories at all.

That said, mezcal makes a superb cocktail. A mezcal Margarita has a depth its tequila cousin can only dream of, and a mezcal Negroni or an Oaxacan Old Fashioned turns the smoke into something autumnal and grown-up. Use your everyday bottle for mixing, and save the rare stuff for the copita.

Where to start

If you buy one bottle to understand what mezcal is, make it Del Maguey Vida. Made by the Cruz family in San Luis del Rio from one hundred per cent espadin, it was built to bridge the gap: traditional enough to be the real thing, approachable enough to mix. Campfire smoke, charred pineapple, a lick of leather and sage, all at a gentle forty-two per cent. It is the bottle bartenders reach for, and the best possible first handshake with the category.

When you are ready to go off the map, Lost Explorer Wild Salmiana is the next chapter. Its agave, the wild maguey verde, grows at altitude and takes around twelve years to mature before maestro mezcalero Fortino Ramos ever touches it. The result is brighter and stranger than the espadin: green chilli, grapefruit, thyme and a mineral edge, with the smoke kept clean and low. One is the introduction. The other is the rabbit hole.

Buy them together and you have the whole story in two glasses: the benchmark and the wild card, the drink you learn on and the drink you graduate to.

So which is better?

Neither, of course, which is the only honest answer. Tequila is the drink of the party: bright, quick, sociable, brilliant in a Paloma on a warm evening. Mezcal is the drink of the conversation that carries on after the party, when the fire is lit and nobody is in a hurry. They are siblings, not rivals, and any cabinet worth the name has room for both.

So the next time someone reaches for the shot glass, gently move it out of the way. Pour them a thimble of something smoky instead, tell them to take their time, and watch the wince turn into a question. That question is where the fun begins.