"Reverse steaming", also known as "three steaming and three drying", is a special production method of dried sweet potatoes. Reverse steaming refers to exposing the sweet potato steamed once or twice to the sun, and then putting it back into the steamer to continue steaming. Why do you want to use this production method? Isn't it troublesome to do so? Dried sweet potatoes made by ancient reverse steaming are sweet and chewy, q-elastic, not sticky, and the more chewy they are, the more fragrant they are. After eating, you will know that although this processing method is tedious and time-consuming, it is really worthwhile. The "three steaming and three drying" of dried sweet potatoes have different uses, one is steamed, the other is steamed sweet, and the third is steamed soft. Therefore, three steaming and three drying are indispensable. The production process of "three steaming and three drying" dried sweet potatoes is quite complicated, including wetting, washing, cooking, slicing, drying in the sun, steaming again, drying again, steaming again and drying again. Because it is cooked and dried in the sun, and then steamed twice, it is named "reverse steaming ancient method" and is also listed as a national intangible cultural heritage.