The evenings have started to close in, which means the drinks have started to change. The spritz has done its summer service and gone quietly back in its box. The tonic water is losing its urgency. And into the gap steps the coldest, most exacting drink in the whole canon: two ingredients, no garnish worth hiding behind, and absolutely nowhere for a mistake to go. The Martini is the hardest simple thing you can make, and autumn is precisely when you should start trying.

There is a reason bartenders talk about it the way pianists talk about scales. This year the Dry Martini sits at number four on Drinks International's list of the bestselling classic cocktails at the world's best bars, in the same rarefied company as the Negroni that tops it. It has been in that top handful for years. A drink with two ingredients has no business being that consistently loved, and yet here we are, ordering them by the coupe in every serious bar from Mayfair to Manhattan.

The good news is that the whole thing is buildable at home in under a minute. The better news is that getting it right is less about kit and more about a few small decisions, made in the right order and with a bit of nerve. Here is how to make one worth sitting down for.

Gin or vodka

Start here, because everything downstream depends on it. The original Martini was a gin drink, and gin is still the answer if you want the cocktail to actually taste of something. A good London Dry brings juniper, citrus peel, a whisper of something herbal: structure, in other words. It gives the drink a spine to lean on. Sipsmith London Dry Gin is the textbook choice, classical and juniper-led and made for exactly this. If you want to trade up into something silkier, Tanqueray No. Ten is distilled around whole fresh citrus and makes a Martini that practically glows.

Vodka is the other road, and it is not the lazy one, whatever the purists mutter. A vodka Martini is colder, cleaner, more about texture than flavour: less a conversation, more a held note. Done well it is glassy and almost viscous, the kind of thing that makes you sit up straighter. Belvedere Organic Vodka is rye-based, which means it carries a faint peppery weight rather than tasting of nothing at all, and that little bit of body is exactly what a vodka Martini needs to stop it feeling like cold water dressed up for the evening.

Neither is wrong. Gin if you want the drink to have an opinion; vodka if you want it to have a temperature. Most people, over a lifetime, end up wanting both, depending on the week.

The vermouth question

Here is where most home Martinis quietly fall apart. Vermouth is not a splash of something you add to be polite. It is the second ingredient in a two-ingredient drink, which makes it fifty per cent of the plot. A classic Dry Martini leans on a French-style dry vermouth, crisp and faintly bitter, and the amount you use is the single biggest lever you have.

There is also a softer, rather fashionable route, which is to reach for a blanc vermouth instead. Dolin Blanc, made in Chambéry by a house that has been at it since 1821, is floral and gently honeyed rather than bone dry, and it turns out a Martini that is rounder and more forgiving: the sort of drink you could serve someone who thinks they don't like Martinis and watch them change their mind.

Whatever you choose, treat it like the wine it essentially is. Vermouth is fortified wine, which means it goes tired and flat once it is open. Keep the bottle in the fridge, not the cupboard, and don't nurse the same one for two years like a sad souvenir. A fresh vermouth is the difference between a Martini that sings and one that shrugs.

Wet, dry, or bone dry

The ratio is the whole personality of the drink, and it lives on a sliding scale. A wet Martini runs at around three parts spirit to one part vermouth: softer, rounder, more openly wine-like, and honestly where most people are happiest even if they'd never admit it. A dry Martini pushes closer to six to one, all steel and clarity. A bone-dry Martini is barely a rumour of vermouth at all: a rinse around the glass, tipped out, then spirit poured over the ghost of it.

The fashionable middle ground, and the one worth learning first, is the fifty-fifty: equal parts vermouth and spirit, stirred long and served very cold. It sounds heretical to anyone raised on the idea that dryer is classier, but a good fifty-fifty is a revelation. Lower in alcohol, more complex, and infinitely more drinkable across a long evening. If you only try one new thing this autumn, try that.

The point is that there is no correct ratio, only your ratio. The professional trick is simply to make it the same way twice, notice what you preferred, and adjust by a splash next time. That is the entire secret. Everything else is theatre.

Stirred, not shaken

Ignore the most famous drinks order in cinema. A Martini should be stirred, not shaken, and the reason is texture. Shaking whips air and shards of ice through the drink, leaving it cloudy, over-diluted, and prickly on the tongue. Stirring chills and dilutes it gently, and leaves it clear and silken: the way a Martini is supposed to feel as it goes down.

Fill a jug or a mixing glass with plenty of ice, more than looks sensible. Pour your spirit and vermouth over it. Then stir, properly, for longer than you think: thirty seconds, maybe forty, until the outside of the glass is painfully cold to hold.

That long stir is doing two jobs at once. It is dropping the temperature toward the near-freezing point a Martini wants to live at, and it is adding a small, deliberate amount of water. That dilution is not a flaw. It is what softens the alcohol and pulls the flavours open. An under-stirred Martini is hot and harsh; a well-stirred one is cold and round. The ice is not a garnish. It is the engine.

Olive or twist

Now the fun part, and the one people get needlessly precious about. A lemon twist is the classic finish: pare a strip of peel, twist it hard over the surface to spray the oils across the top of the drink, run it round the rim, and drop it in. It brightens everything and lifts the aromatics off the glass before you have even taken a sip.

An olive, or three, sends the drink somewhere saltier and more savoury, a proper aperitif that makes you hungry for dinner. Go one further and add a small spoon of the olive brine and you have a Dirty Martini, which is either the best thing that ever happened to the drink or a minor act of vandalism, depending on who you ask. Try it once and pick a side. And if you swap the garnish for a pickled cocktail onion, congratulations: you have quietly made a Gibson, and you sound very sophisticated ordering one.

There is no wrong answer here, only preference. The only genuine mistake is a tired garnish: a twist cut yesterday, an olive that has been open since spring. Fresh, or don't bother.

The glass, and the moment

Chill the glass. This is the step everyone skips and everyone should not. Five minutes in the freezer, or a fill of ice and water while you build the drink, then tip it out. A Martini poured into a warm glass is already dying; a Martini poured into a frosted one holds its nerve to the last sip.

Pour small. A Martini is meant to be drunk cold and drunk soon, so a modest measure that stays icy beats a brimming one that goes lukewarm halfway down. If you want the drink without any of the labour, a bottled option like the Tayēr Sandalwood Martini, from one of London's best bars, does the stirring for you and lives happily in the freezer until wanted.

Then sit down with it. That is the whole ritual, and it is a good one. A Martini is not a drink you carry around a party; it is a drink you stop for. Made properly, in the cold half of the year, with the light going early and something quiet on the stereo, it is about as close as two ingredients ever get to an occasion. Get the order right, stir like you mean it, and you will never look at the spritz the same way again.