What is "grass jelly"

n. A jellylike dessert drink found in China, Taiwan and Southeast Asia, made by boiling grass or leaves of the mint family with potassium carbonate, and then cooling the liquid to a jelly-like consistency.

Grass jelly, or leaf jelly, is a jelly-like dessert found in China, Hong Kong, Macau, Southeast Asia and Taiwan. It is available in various form, size and packages. It is most typically served chilled in a bowl, either by itself or with fruits, but also used in bubble tea. Outside of Asia, however, it is mostly sold in cans or packets in Asian supermarkets.