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Emeralds or Rubies

This is a popular Southeast Asian dessert featuring water chestnuts coated in tapioca and served with fruits and sweetened coconut milk.

The water chestnut is soaked in water and food color and takes on that color. Its tapioca coating gives it a gemstone sheen lending it, its name tup tim, which translates to rubies. This also tells us that it is traditionally soaked in red food coloring. I’m not sure if it’s because I just re-watched The Wizard of Oz, but I felt a little green. So I made this green version, which I am calling emeralds aka morakot.

They do give a nice crunch and is different in texture of many of the other components, one can find in nam wan, which is the cocktail as a whole with sweetened coconut milk. I’m almost tempted to do a nam wan series. It is a very versatile and highly customize-able dessert, which could be why so many people love it.


  • The longer you soak the water chestnuts, the dark the color. If you want pink for an event like girly baby shower, use the red food color, but don’t soak it too long.
  • You can use either tapioca starch or corn  starch.
  • Cut the water chestnut to whatever size you want. I had large chopped, which are great for crunch factor, but at the same time the tapioca can be chewy. If they are too big, they could be like a tough boba at the bottom of your drink.
  • When dropping the starch coated chestnuts into the boiling water, make sure to break them up. If they get stuck together, you’ll have clumps of gemstones. Don’t say I didn’t warn you.
  • If desired, you can add a drop or two of jasmine or pandan extract into the sweetened coconut milk syrup, but do just that…a drop of two. Less is more.
Emeralds or Rubies (Tup Tim)

1 (8 oz) can whole water chestnuts
1 teaspoon red or green food coloring
1 cup water
½ cup tapioca starch

Sweetened Coconut Milk
1 (13.5 oz) coconut milk
½ cup sugar
½ cup water
½ teaspoon salt

Optionally, served with fruits, palm fruit, jellies and crushed ice.

  • Drain and chop water chestnuts into small pieces and place in small bowl. Sprinkle food coloring on the water chestnuts pieces. Use red food coloring for the traditional rubies. Mix the color in. Then pour about 1 cup of water, enough to cover the water chestnut. Let it soak for 30 minutes to an hour.
  • Strain the water chestnuts and toss in tapioca or corn starch. Make sure they are completely coated on all sides. Using a strainer or slotted spoon to sift the excess starch from the chestnuts.
  • In a medium sauce pan, bring water to a rapid boil. In small batches, boil the starch coated water chestnuts for 3-4 minutes or until they float to the top. Using a slotted spoon remove from boiling water and immediately dunk into iced/cold water. Allow to cool for a minute or two before removing from water. Continue to boil small batches until you run out.
  • For sweetened coconut milk. In small sauce pan, bring sugar, salt and water to a boil until sugar is completely dissolved a mixture thickens slightly into syrup. Turn off heat and allow to cool. Stir in coconut milk before serving.
  • Serve with crushed ice, fruits, palm fruits and jellies.


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