Write Zhou Ningwu's composition.

Wu Guodan is one of the unique Han snacks in Zhouning, Fujian. Zhouning dialect calls potatoes "black eggs", so potatoes are the main raw materials for making black eggs. Because the potatoes in Zhouning are more sticky than those in other places, they can be made into potato cakes with a knife like patting dough after being cooked, while the potatoes in other places are scattered as soon as they are patted, which has become the characteristic of Zhouning potatoes. It is to cook potatoes, peel them, pat them into mud, knead them evenly with sweet potato powder, and spread them into cakes to form a black egg shell. Cut into thin slices about two centimeters wide and five centimeters long, and add ingredients such as sauerkraut, vegetables, minced meat, shrimp, bean paste and pepper. And cooked or fried.