If you have a flat grater, grate the beet directly into the water until the colour intensity is the way you like it. If you have a box grater, grate about ¼ of a medium beet and put it into the water. Stir to extract the colour and strain the liquid into a small pot, pressing out all the water.
1 ¼ cups water, A quarter of a beet
Stir in mung bean starch, tapioca starch, sugar, and flavouring of your choice, if using; stir until the starch is all dissolved.
¼ teaspoon Jasmine extract or coconut extract, 3 tablespoon mung bean starch, 1 tablespoon tapioca starch, ⅓ cup + 1 tablespoon sugar
Turn the heat on medium and stir constantly with a rubber spatula. As the mixture heats up, it'll gel up bit by bit. Keep stirring constantly until the whole mixture has become thick and translucent. Once the mixture doesn’t look like it’s changing for a good 15 seconds, the pudding has fully cooked. Add the water chestnuts and stir for another minute to allow the mixture to heat back up before turning off the heat.
1 cup cooked or canned water chestnuts
Right away, spoon the pudding over the coconut layer, aiming for roughly the same amount for each layer. If for some reason the mixture has cooled down and become too stiff to spoon, simply heat it back up while stirring constantly over medium heat to soften it.
Allow the pudding to cool to room temp before serving. (See storage notes in the blog post.)