British Prime Minister Keir Starmer's visit to Shanghai's Yuyuan Garden during his recent trip to China has thrust a local pastry into the global spotlight.

While visiting the nearly five-century-old landmark, Starmer bought a box of hudiesu — a local interpretation of the French confection the palmier — from Lu Bo Lang, a restaurant specializing in Shanghai cuisine.

The British prime minister paid 48 yuan ($6.90) for eight palm-sized pieces of the butterfly-shaped treat, which set social media both in China and abroad abuzz overnight.

The restaurant normally sells around 100 boxes of its hudiesu daily. However, a Lu Bo Lang staff member who asked to remain anonymous told China Daily: "After the prime minister's visit, customers came in one after another. Our daily sales reached around 300 boxes."

But locals were left perplexed at the fuss being made over Starmer's pastry purchase, as hudiesu has, for a long time, been one of the best gifts to give friends looking for a taste of Shanghai. It's the willingness to wait in long lines to buy them that makes the gesture truly precious.

As one of Shanghai's most iconic pastries, the crispy and flaky delectation is a delightful blend of Chinese and Western culinary influences, and is the perfect accompaniment to a cup of coffee or tea. Unlike palmiers found in northern Chinese cities, which are usually smaller and harder, Shanghai-style hudiesu are very buttery, light and flaky.

"It's all about the proportion of flour and butter," Lin Jianming, a veteran pastry chef, told China Daily in an earlier interview.

Although the palmier originated in Europe around the 1930s and is sometimes referred to as "the heart of France", it underwent a local transformation and quickly became a unique Shanghai treat.

Wu Jianglei, manager of Park Hotel Bakery, said: "Based on the traditional French craftsmanship, we reduce the sugar content by 50 percent to highlight the aroma of the butter, transforming the product's taste from hard, crispy and sweet to soft, fluffy and fragrant."

The Park Hotel Bakery's palmier is undoubtedly the most favored in the city. In 2021, the bakery's recipe and process were listed as an intangible cultural heritage item in Shanghai's Huangpu district, where the hotel is located.

Wu said that the palmier was introduced to the Park Hotel when it opened in 1934. Originally named "Ear Cake", it was exclusively served as dim sum during the hotel's afternoon tea service. In the 1980s, the hotel began selling the pastry to the public, and it quickly became popular among locals.

"This miniature embodiment of the fusion of Chinese and Western cultures vividly symbolizes the city's openness and inclusiveness," Wu said.

However, getting a box of the freshly made treats requires time and patience.

While Starmer was able to skip the line at Lu Bo Lang, the line outside the Park Hotel Bakery is far more daunting. The bakery is open from 8 am to 8 pm, and by 7:30 am, there is already a long line of hungry customers. At that time, the wait is about an hour. In the afternoon, it extends to at least two-and-a-half hours.

There is a clear note inside the bakery: "To ensure everyone gets our palmiers, each person is limited to six packs a day. Thank you!"

The hotel says daily sales of the pastry can reach 7,500 packs, and many customers are foreigners.

"I got here at 2 pm, and three hours later, I got them! I tried one immediately. … Wow! Definitely worth the wait," said Mike Brown, a visitor from the United States.

Wu, the bakery manager, said: "Now, we have a more international clientele, and they recognize our products well. I believe the palmier pastry represents a significant cultural and economic phenomenon of our time."