The dough is then flattened and cut into slices that are as thick as a deck of cards before they are placed in the oven. Timing is crucial as it determines whether the pastry turns out soggy or crispy.

The bakery at Park Hotel, opened in the 1930s and once the tallest building in east China, is one of the first in Shanghai to offer the butterfly pastry. For many senior citizens, sipping a cup of coffee while eating the pastry at the hotel’s art-deco lobby was something of an indulgence in the golden days.

According to the salespeople at Park Hotel and Deda, the majority of those who buy the butterfly pastry now are from the younger generations.

The butterfly effect has also rippled to places outside Shanghai. On Taobao.com, China’s largest customer-to-customer online shopping platform, people from other Chinese cities are paying almost 50 percent more to have the delicate pastry packed and shipped to their homes.

According to Liang Jianzhou, chief director of Park Hotel’s cultural affairs office, the butterfly pastry has also been chosen as the treat for first-class passengers on high-speed trains between Shanghai and Beijing.

xujunqian@chinadaily.com.cn