Kuzuko

Kuzuko (葛粉^?) or Got Fan is a starch powder made from the root of the kudzu plant. It is traditionally used in Japanese cuisine and Chinese cuisine mainly for thickening sauces and making various types of desserts.

Examples of dishes that use kuzuko:

Examples of wagashi (Japanese desserts) with kuzuko:

Examples of Tong sui (Chinese desserts usually in soup form)

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Wikipedia