Penicillin

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What Is a Penicillin?

The Penicillin is widely regarded as the most successful cocktail invented in the 21st century: blended Scotch whisky, honey-ginger syrup, and fresh lemon juice, topped with a float of intensely peaty Islay Scotch that delivers smoky aroma before the first sip even happens. It's a masterclass in layered balance — smoky, sweet, spicy, and tart all at once — and it belongs to the same whisky-sour lineage as the site's Whisky Sour, though its ginger-honey syrup and Islay float push it into far more complex territory.

The History Behind the Penicillin

The Penicillin was created in 2005 by Sam Ross, an Australian bartender working at Milk & Honey, the legendary and influential speakeasy-style New York bar founded by Sasha Petraske — just a year after Ross had emigrated from Melbourne. Ross built the drink as a direct riff on the Gold Rush, an earlier Milk & Honey creation by bartender T.J. Siegal that combined bourbon, honey syrup, and lemon juice into a simple, elegant sour. Ross swapped the bourbon for mellow blended Scotch, then cut the honey with fresh ginger juice for extra spice, having been inspired after experimenting with Compass Box's Peat Monster, a rich, smoky blended Scotch he'd been playing with behind the bar. To finish the drink, he added just a quarter-ounce float of intensely peaty Islay single malt on top, turning a good cocktail into an unforgettable one — the smoky aroma hits first, well before the layered, honey-and-ginger body underneath registers on the palate. The name is a wink at the old idea of good Scotch as medicine, and the drink spread from Milk & Honey to bars worldwide with remarkable speed for something barely two decades old. Ross's current bar, Attaboy, which now occupies the old Milk & Honey space, reportedly serves an even richer 3:1 version of the original ratio, a detail noted in Club Oenologique's breakdown of the Penicillin's construction.

What Does a Penicillin Taste Like?

Blended Scotch provides a smooth, honeyed base with mild smoke and grain sweetness, while the honey-ginger syrup adds warm spice and body that feels substantially more complex than plain honey syrup alone. Fresh lemon juice supplies the acidity needed to keep the drink from tasting heavy or one-note. The floated Islay Scotch — typically something intensely peaty like Laphroaig — sits on top rather than mixing in fully, so the first thing a drinker encounters is a wave of smoky, maritime, almost medicinal aroma before tasting the sweeter, spicier layers underneath. That aromatic contrast between the smoky top note and the honeyed, gingery body is the Penicillin's defining feature, and it's part of why the drink feels so much more layered than a standard whiskey sour.

How to Make a Penicillin

First, make honey-ginger syrup by combining honey, water, and fresh ginger juice (pressed or grated and strained) until smooth. Shake 2 oz blended Scotch, 0.75 oz fresh lemon juice, and 0.75 oz honey-ginger syrup with ice until well chilled, then strain into a rocks glass over fresh ice. Float 0.25 oz peaty Islay Scotch on top by pouring it slowly over the back of a spoon, so it sits as a distinct layer rather than fully incorporating. No garnish is strictly required, though a piece of candied ginger is a common addition.

Popular Variations

The Penicillin's structure has inspired plenty of modern riffs. The Oaxacan Penicillin swaps the blended Scotch base for reposado tequila and replaces the Islay float with smoky mezcal, trading Scotland's peat for Mexico's agave smoke while keeping the same honey-ginger-lemon backbone. A "Penicillin Sour" version replaces the Scotch with bourbon or rye, moving the drink closer to its Gold Rush ancestor while keeping the ginger spice that makes the Penicillin distinct — a similar ginger-and-whiskey pairing to the one found in the site's own Irish Whiskey Ginger. For colder months, a Hot Penicillin skips the ice entirely, building the same ingredients in a heatproof glass topped with hot water for a warming, toddy-like variation, one of several riffs catalogued by PUNCH's Penicillin recipe.

Glassware, Garnish, and When to Serve It

A rocks glass over a single large ice cube is the standard serve, allowing the drink to stay cold without diluting too quickly as its layered aromas develop. Candied ginger is the most common garnish, though the drink is often served unadorned to let the Islay float's aroma take full focus. It's a sipping cocktail suited to cooler evenings and serious cocktail bars, occupying similar contemplative territory to the site's Old Fashioned, spiced Gingerbread Old Fashioned, and honeyed Maple Bourbon Sour.

Why the Penicillin Became a Modern Classic So Fast

Few cocktails invented in the last twenty years have achieved the near-universal bar menu presence the Penicillin now enjoys, and its rapid rise says a lot about what made Milk & Honey's late-2000s cocktail scene so influential. The drink takes an already-excellent modern classic, the Gold Rush, and adds a single inspired twist — the peaty Islay float — that transforms the entire drinking experience without complicating the build. That combination of simplicity and genuine innovation is exactly why bartenders adopted it so quickly, and why it now sits comfortably alongside genuine century-old classics covered in the site's guide to the best bourbon cocktails for whiskey lovers, despite being barely old enough to legally drink itself, a modern rival to the equally cult-favorite Last Word in the pantheon of bartender-revived classics.