Blimey, this drink looked familiar. The setting was a maritime pub in the pretty village of Wyk on the island of Föhr, a gateway to the North Frisian Islands on Germany’s North Sea coast. Propped at the bar was Jann-Oluf Arfsten, aka “Mr Manhattan”, a vegetable and potato farmer, now in his 50s, who was slowly sipping a glass of maple-brown alcohol known as “the national drink of Föhr”. “Every day is better with one of these,” he said, shaking hands. “Come on in.”

The Manhattan is a longstanding tradition here and everyone grew up with it

Think of the drink as a North Frisian version of a classic New York cocktail and it may sound familiar. One-part whisky to one-part sweet vermouth and one-part dry vermouth, it’s a finely-tuned take on a traditional Manhattan, served without Angostura bitters or ice, in a well-used rocks glass.

This homemade cocktail has been sold pre-mixed from behind the bar at Glaube Liebe Hoffnung for decades, and not a week goes by without the old timers’ pub exhausting around five litres of its cult supply – which is a discernible amount in a nation of obsessive beer drinkers and on an island with a population of only 8,000.

Arfsten nodded to barkeep Andreas Hansen, who produced a label-less, chilled bottle and two more tumblers. One for me, the other for the barman. It was an unexpected welcome, and soon the aperitifs were garnished with maraschino cherries spiked through the midriff with cocktail sticks. A moment later, our glasses were empty.

“Would you like another?” asked Hansen, hovering nearby with the bottle in hand, which he had topped up from a glass demijohn filled with the premixed liquid. “The Manhattan is a longstanding tradition here and everyone grew up with it. Weddings, funerals, parties, christenings – we drink one at almost every occasion. And some people can drink a dozen in one go easily. Why? Because of nostalgia, I guess.”

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Mr Manhattan had his farm to attend to – asking me to drop by to see him the following morning – and so I found myself wondering about Föhr and its nostalgia for a cocktail born half a world away in New York City. The world is filled with people who have never heard of a Manhattan, let alone had the desire to drink one, but there are others who not only know the well-crafted cocktail well, but treat it with such religious fervour that it is sacred like holy water. Such fanatics might only be found on Föhr.

Where, though, did this obsession come from?

If you want to understand Föhr and its love of the Manhattan, you have to make sense of the island’s distinctive geography and backstory. Long before the cult drink gripped the island’s subconscious, Föhr was little more than an island of farmers and fishermen, a downbeat community 10km from the mainland, where the way of life was shaped by the land, the North Sea and the elements. Money was scarce, work scarcer still, and the workforce took to whaling.

The whaling industry, which stretched from New Bedford and Nantucket in Massachusetts to Tasmania, Australia, collapsed in the late 19th-Century, and Föhr’s whalers were put out of business. Wave after wave of emigration followed. First to Hamburg, 200km to the south, then, to America, 6,000km away, where fortune awaited. Some felt the gravitational pull of the gold rush in California, but the majority stayed on the US’ east coast. Soon, the Big Apple was brimming with North Sea refugees.

Soon, new family businesses were flourishing across the Atlantic. German delis opened in Brooklyn; bakeries appeared in the Bronx; and, crucially, bartenders learnt the art of the aperitif in Manhattan. Around this time, circa the 1880s, an in-demand party drink using rye whiskey, a sweet vermouth modifier and bitters was invented in New York’s Manhattan Club (contrarily, another legend claims this a myth and that the drink was, in fact, invented at the Hoffman House in the 1870s). Coincidence that this cocktail recipe eventually travelled back across the Atlantic? Not likely.

Away from Wyk’s pubs and bars – out on countryside roads, past the 13th-Century Frisian Cathedral, where you can see the tombstones of whalers – it’s easy to get a feel for what keeps the Frisians tied to Föhr. There are sweeping beaches, shallow seas and quaint thatched houses and farmsteads unchanged since medieval times. But this is accompanied by the occasional yowling of the North Sea and the kind of biblical rain that’d make Noah rush for the boatyard.

Even so, Föhr is also the kind of place that lends itself to flights of fancy, like me showing up at a farmhouse on a whim, just before dark, and in the hope of finding out more answers. As I knew Arfsten was busy, I rang the doorbell of Jan Robert Hinrichsen, whose well-tended cattle farm on the west coast is also home to Hinrichsens Inselwhisky, the island’s first and only whisky distillery. I’d heard talk about his new venture and it seemed likely he’d know more.

Hinrichsen told me that in 1865 his great-great-grandfather, Hinrich Cornelius, joined the Frisian exodus to New York, returning 15 years later to bring money back to the family farm. In keeping with tradition, his son then took a ship to America in 1905 to become a barkeep, with his heir – Jan Hinrichsen’s father – born in the Bronx, before the family returned to Föhr in 1959.

“My father kept his American accent until the day he died,” Hinrichsen said, leading us from twilight-lit barley fields into a hangar-sized cattle barn home to his newly launched distillery. “He was always homesick for New York but was Frisian at heart. I remember him saying it was easier for a Frisian to feel welcome in New York than in Bavaria.”

With such a tight-knit connection between the two places, it’s not hard to imagine Frisians returning to Germany and bringing their love of New York bar culture with them. “We’re party people at heart, so it made sense,” said Hinrichsen, tapping a cask and offering me a two-year-old dram of whisky for a tasting. “This island endured hard years of whaling and farming, and drinking became part of our social fabric. From birth to death, it’s part of who we are.”

The next day, I arrived at the Arfsten farmstead to be greeted not by Jann-Oluf but his wife Beate, who I later learned was the architect behind much of the Manhattan’s modern-day renaissance. “The premixed cocktail mixture was my husband’s idea,” she said, leaning forward as if telling me a secret, “but somehow I’ve ended up doing all the hard work.”

Given Föhr’s history of intemperance, it really shouldn’t have been a surprise that the husband-wife team had a fully stocked, beautifully crafted, wooden counter bar in their home. More than that, though, were piled-high crates of branded “Föhrer Manhattan Cocktail”, which they’ve premixed and packaged at home for the past 20 years. On the label of the pop-top bottles was the New York of the millennium, before the World Trade Center’s two towers fell, with a skyline as powerful and stirring as the contents. Astonishingly, Beate told me, the couple sell more than 6,000 bottles every year to islanders and tourists.

The biggest surprise was that the Manhattan home-blend was born on a whim. For ease and convenience, Beate said, Jann-Oluf and two friends were frustrated by mixing their own Manhattans at home and wanted a bottle they could simply pull straight from the refrigerator. Almost overnight, northern Germany’s unlikeliest souvenir was born, and to this day almost every house on Föhr has a bottle of the concoction in cold storage. “It’s like learning the secret recipe for Coca Cola,” said Beate, of the blending process. “Balance, taste, the right mix – that’s why we sell out our entire stock every year.”

Make no mistake: there’s more to Föhr’s obsession with the Manhattan than the right blend of whisky and vermouth. Perhaps, I thought, its popularity also had to do with the cold, harsh weather in winter and the warm hangover of summer that’s also characteristic of New York. The never-ending movement of people coming and going. It was tempting to reach for metaphors, but then I lost my track of thought.

“Would you like a drink before you go?” asked Beate, filling a tumbler without reply. I looked at the Manhattan on the table, the presence of the glass magnified by the heavy silence in the room around us. It would have been very rude not to accept it. Especially not here.

Islands of Imagination is a BBC Travel series that journeys to some of the world’s most unique, extreme and beautiful places that have been inimitably fashioned by their geographic isolation.

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