Buy a flat-bottomed cast iron pot online, 27~30 cm. Put the pot on the stove and heat it with 800 watts. When the palm feels very hot above the bottom of the pot, the cold oil soaks the whole bottom of the pot. Immediately pour in the batter or spread the green embryo of the cake in a circle. After spreading the flat paste, turn it over when the surface of the dough keeps bubbling and the edge of the cake hardens, and immediately adjust the firepower to 300 watts. When the cake stops bubbling or the bottom slightly smokes, turn off the fire and take it out.