Walk into almost any Chinese restau­rant in Britain and it’s likely crispy seaweed will be on the menu, alongside crispy aromatic duck.

Most diners, though – those of Chinese descent included – are unaware of what the dish actually is. Not seaweed, as the name suggests, it is instead terrestrial greens, such as bak choi or collards, cut into thin strands, dried and deep fried.

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The dish is so widespread that Ken Hom, who made his career in Britain as a television chef and cookbook author, has included a recipe for it in at least two of his books, as well as his 2000 TV series, Foolproof Chinese Cookery. The American-Chinese chef acknowledges that it’s a British invention, but in his Complete Chinese Cookbook, published in 2011, Hom says of the dish, “I am not sure who was the first to bring this unique eastern-northern Chinese dish to England; suffice it to say, however, that not ‘seaweed’ but cabbage is now being used. The special type of seaweed which is indeed used in China is unfortunately not yet available in the UK or the West. The adaptability of Chinese cuisine is once again demonstrated in this dish: if the original ingredients are not available, technique and ingenuity will overcome the deficiency.”

The Chinese dish Hom references may be deep-fried peanuts and tai cai, an algae known as Enteromorpha linza, which is popular as a snack or appetiser in eastern Zhejiang province.

The Zhejiang port of Ningbo was one of the initial five to open to British trade after the first opium war (1839-1842), although, according to John A. G. Roberts, author of the book China to Chinatown: Chinese Food in the West, the British and the Chinese lived very separate lives.

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It wasn’t until just before the second world war that Chinese seamen began opening over­seas restaurants serving food from their home­towns, including Ningbo, which may have planted the seed for this now ubiquitous British-Chinese dish.

Chinese restaurateurs in Britain pandered to the tastes of the local clientele and deep-fried foods fared well, another “classic”, crispy aromatic duck, also proving popular. Crispy aromatic duck is comparable to a dish with a similar name, xiang su ya, eaten throughout Sichuan, Jiangsu and Hunan. However, in Britain, it is served with pancakes and condi­ments such as hoisin sauce, Chinese leek and cucumber – accom­paniments normally associated with Peking duck.

In an interview with the Ming-Ai (London) Institute, Liu Yu-ching, a British-Chinese chef and promoter of Chinese culture, notes that Peking duck was first served in Britain as late as 1963, when the city’s first Pekingese restaurant, Kuo Yuan, opened in northwest London. Crispy aromatic duck had arrived earlier.

Michelle Ng, the Hong Kong-based food blogger behind Chopstixfix, who grew up in North London, observes, half jokingly, that “everyone was just obsessed with the pancake element”. Which might explain how the two duck dishes became conflated on British menus.