Grass jelly is made by boiling the aged and slightly oxidized stalks and leaves of Platostoma palustre (Mesona chinensis) with potassium carbonate for several hours with a little starch and then cooling the liquid to a jelly-like consistency.This jelly can be cut into cubes or other forms, and then mixed with syrup to produce a drink or dessert thought to have cooling (yin) properties, which makes it typically consumed during hot weather. The jelly itself is fragrant, with a smoky undertone,and is a translucent dark brown, sometimes perceived to be black. Food coloring may sometimes be added to make it darker.