Why a Moscow Mule needs ginger beer, not ginger ale: the spec and a mule builder

The Moscow Mule is three things in a mug: vodka, ginger beer and lime. It looks like nothing, and that is why the details matter. Pick the wrong fizzy ginger drink and it tastes like a sweet soda with a kick. Pick the right one and the ginger bites back at the lime. Here is the spec, the one choice that changes the drink most, and a builder so you can see what each pour does.

The spec

Method: built, not shaken. Fill a mug or rocks glass with ice, add the vodka and ginger beer, then the lime juice, and give it one gentle stir. Shaking anything fizzy knocks the bubbles out, and there is nothing in this drink that needs shaking. Glass: the classic copper mug, or a rocks glass, or a tall glass for a longer drink.

Build one, see the numbers

Ginger beer, not ginger ale

This is the choice that changes the drink most. Ginger ale is a mild, sweet, fizzy soft drink with a hint of ginger. Ginger beer is usually spicier, and the ginger tastes like ginger rather than a flavour. The Mule is named after the kick, so you want that bite. Styles vary a lot between brands, from fiery and cloudy to sweet and pale, so taste your ginger beer on its own first. If it is sweet and mild, add the extra 5 ml of lime. If it is dry and hot, stay with 10 ml.

Ginger beer here means the soft drink. Some old-style ginger beers are lightly fermented and contain a little alcohol, so check the label if you are making the alcohol-free version.

Why the copper mug, and a safety note

The mug is partly practical and partly marketing. Copper conducts heat well, so a mug filled with ice feels cold in the hand almost at once, and the rim frosts over. The popular story is that John G. Martin, who sold Smirnoff vodka in the United States, had bartenders photograph themselves with a copper mug and a bottle to promote the drink. Like most cocktail origin stories, this is contested: the usual account puts the drink's creation in 1941 at the Chatham Hotel in New York, involving Jack Morgan of Cock 'n' Bull ginger beer and Martin, while a later account credits a bartender called Wes Price, who said the drink was a way to use up surplus vodka and ginger beer. Nobody can prove either, so treat both as stories.

One safety point is real. Lime and ginger beer are acidic, and the US Food Code says copper should not touch foods with a pH below 6. In 2017 the Iowa Alcoholic Beverages Division warned against serving acidic drinks in pure, unlined copper mugs. Mugs lined with nickel or stainless steel are fine, and so is a plain glass. Some scientists point out that short contact times carry little risk, but a lined mug costs nothing extra, so choose one.

The Mule is a ginger drink with a vodka backbone, not a vodka drink with some ginger in it.

Variations, including alcohol-free

Virgin Mule: 150 ml ginger beer and 15 ml lime juice over ice, in the same mug. Add a few mint leaves slapped in your palm for scent. The lime does the job the vodka's dryness did, so it needs a little more than the standard measure.

Kentucky Mule: swap the vodka for 45 ml of bourbon. Mexican Mule: use a blanco tequila. London Mule: use a London dry gin. All of them keep the 1 to 2.5 to 3 ratio. Whatever you use, a Mule is a long drink: pour once, sip slowly and have water alongside.

What to look for

• A real ginger bite. Taste the ginger beer on its own. It should taste of ginger, not just sweetness.
• Fresh lime. Bottled juice is flat. Squeeze it just before you pour.
• Plenty of cold, hard ice. Fill the mug to the top. Cold ice melts slower, so the drink stays fizzy and the ratio holds.
• A lined mug or a glass. See the safety note above.

Please drink responsibly, and not if you are driving. Cocktails are for adults only.