They cannot be replaced because their respective purposes and usage are inconsistent. 1. Uses of cornstarch 1. Cornstarch is a term that often appears in recipes. It is mostly used to thicken gravy. The cornstarch used in mainland China is potato starch, the cornstarch used in Hong Kong is corn flour, and the cornstarch commonly used in Taiwan is gordon flour. It is Taibai powder, which is made from potatoes or cassava.