Start by adding in your grass jelly powder to a pot along with the water.
Whisk everything well together and then let it sit and bloom for about 10 minutes.
Next, heat up the pot over medium heat while constantly stirring the mixture.
After a few minutes, you will notice that the grass jelly has become very lumpy. Continue whisking it, making sure to also scrape the bottom of the pot to prevent it from sticking to the pot.
After a few more minutes, the grass jelly will return back into a thick liquid form.
Once the pot starts to boil, turn off the stove, and pour out the grass jelly into a container. I recommend also using a strainer to pour out the grass jelly to remove any lumps, impurities, and bubbles from the grass jelly.
If you see any bubbles then use either a spoon or toothpick to pop or scoop out the bubbles, but make sure to work fast as the grass jelly will start to solidify quickly after being poured out.
Let the grass jelly rest at room temperature until it has solidified and cooled down for a bit and then cover the container and place the grass jelly in the fridge to fully solidify and cool down. Allow the grass jelly to cool in the fridge for at least 4 hours but ideally overnight before serving for the best results. When ready to serve, cut the grass jelly into small cubes.