This technique is a non-material cultural heritage project in Jinghai District. In 1900, a local villager named Cao Guozhang ran a small restaurant and created a dish called "Cao San braised fish". As he was the third son in his family, the dish was named after him. The main ingredient is a two-inch carp, which is fried twice and then mixed with vinegar, soy sauce, scallions, ginger, garlic, fermented tofu, sesame oil, and star anise. The fish is then stacked in a large pot and simmered in water over low heat for 10 hours, with coal ash sealing the stove and 6-7 fire holes open. The braised fish has no bones and the head is tender and crispy, with a unique aroma of soy sauce. It is delicious with rice or as a side dish with alcohol, and is suitable for people of all ages. It is said that after tasting Cao San braised fish in Duliu, the former President of the Republic of China, Cao Kun, praised it highly and awarded Cao Guozhang several hundred silver coins. Nowadays, Cao's descendants continue to make "Cao San braised fish" and have applied for a patent, making it famous both locally and in the distance.