Prepare the required raw materials: half a sweet potato, half a purple potato, 1 egg, appropriate amount of low-gluten flour, and appropriate amount of oil.

Put the sweet potatoes and purple potatoes into a steamer and steam them separately. Beat the steamed sweet potatoes and purple potatoes into a puree and set aside. Divide the eggs into two equal portions and put them into the sweet potatoes and purple potatoes respectively. In a bowl, put the low-gluten flour into the sweet potatoes and purple potatoes respectively. You can also add sugar or milk and other ingredients you like, and then stir evenly. Knead both doughs well and let them rest for 20 minutes. Shape the dough into a flatbread. Place the purple potato dough on top of the sweet potato dough and roll it up.

Put the rolled noodles in the freezer. In order to facilitate the next operation, after freezing, cut them into pieces and set aside. The thickness of the cuts is as thick as the back of the knife. Then put it into the oil pan and fry it until it is cooked and take it out.