I would normally use caramelized brown sugar, and canned grass jelly. It can also be mixed with soy milk to produce a milky white liquid with black strands in it.
Grass jelly is considered a tonic. Grass jelly is made by boiling the aged and slightly fermented stalks and leaves of Mesona chinensis (member of the mint family) 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 properties, which makes it typically consumed during hot weather. The jelly itself has a slight bitter taste, a light iodine lavender flavor, and is a translucent black. (source)
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