DAI HOANG, Vietnam -- With a gas mask on, Bui Van Cuong tends to hundreds of clay pots filled with bubbling braised fish, a traditional delicacy popular in northern Vietnam during the Tet Lunar New Year holiday.

The mask helps Cuong work amid the smoke from the firewood burning beneath the clay pots of black carp that he cooks in the yard of his employer, Tran Duc Phong, in Dai Hoang, a Red River Delta village surrounded by verdant rice fields about 100 km (62 miles) from the capital, Hanoi.

Cuong likes his job, though he admits it’s not easy. The gas mask is a necessary tool, he added: “Without it, I can only work for 15 minutes.”

Dozens of other families prepare fish the same way in Dai Hoang.

Because of its unique flavours, the food’s popularity has gone beyond the village, even reaching Vietnamese communities abroad, buoyed by rising incomes and word spread on social media.

“I provide braised fish to everywhere in Vietnam as well as overseas markets, though mostly the domestic market,” Phong said, standing before dozens of large clay pots, smoke lingering in the air around him.

The most delicious variety, he says, is made with black carp, which is cooked for about 12 hours until tender with firewood from the tropical longan tree, better known for its sweet, juicy fruit.

The black carp, each weighing 4-6 kg (9-13 pounds), are carefully selected and cleaned, cut and marinated, then cooked with a broth made from freshwater crabs mixed with spices, soy sauce, coconut milk and sugar.

A root similar to ginger called galangal is placed on the bottom of the pots to prevent the fish from burning.

Phong and other sellers in the village were inundated with orders ahead of the Lunar New Year, which began on Friday.

He typically makes several hundred clay pots of braised fish each day in the run-up to the holiday, receiving most of the orders online.

“COVID-19 has affected almost all parts of the economy,” said Phong.

“But luckily for me, people still need to eat and they still need braised fish for Tet.”