Fill a mixing bowl with enough water to cover the diced chestnuts. Add food coloring until the water is red to your liking.

Add the water chestnuts and leave them to soak until red, about 20 minutes. Meanwhile, make the sugar syrup and coconut milk (see instructions under "sugar syrup and coconut milk").

Drain the chestnuts and transfer them to a large mixing bowl.

Add tapioca starch to the mixing bowl, mixing well using your hand until each piece of chestnut is coated with tapioca. Shake off extra starch in a strainer.

Cook the rubies by placing them into boiling water, stir gently to prevent sticking. After a short amount of time they will float to the top, at this moment cook for 2 more minutes. Make sure not to overcook.

Remove the rubies from your pan or pot and add them to a bowl of iced water to stop them from cooking. After 2 minutes, transfer them to the prepared coconut syrup.

Sugar syrup: Heat water in a pot over low heat and add sugar. Cook and stir until sugar has dissolved, then chill.

Coconut milk: In a pan or pot over low heat, boil coconut milk, pandan, and salt. Cook for 2–3 minutes and then chill.

Scoop some of the rubies into your serving bowl and add the optional jackfruit and/or young coconut strips. Pour on a generous amount of coconut milk and pile on some crushed ice, enjoy chilled!