Wash the black beauty potatoes, peel them and cook them in boiling water. Put the black potatoes in a large bowl, grind them into paste with a spoon, then add flour, a little salt and chopped green onion, add water and mix well. Put the oil in the pot. After the oil is hot, add the mashed black beauty potatoes, flatten them into round cakes with a spoon, and fry them on medium heat until both sides are slightly yellow. Put the black potato cake on a plate, cut it into 6 pieces of the same size with a knife, and coat each black potato cake with condensed milk and tomato sauce. Can be used as snacks or table food. Regular consumption of black beauty potato pancakes has therapeutic effects of invigorating qi and spleen, appetizing and relaxing bowels.