Khanom Piek Boun | Lao Blackened Rice Cake
What is khanom piek boun | Lao Blackened Rice Cake?
This is one of those rare dishes passed down through oral tradition—hard to find and even harder to make. It’s not often prepared anymore, mainly because of the time and skill it takes to burn the coconut husk and create the activated charcoal that gives the dessert its signature black color. What makes this dish so special is how it uses every part of the coconut: the husk, the flesh, and the milk. Like the Lao dessert khao pahd, it sets into a soft, jiggly consistency.
I first tried this dessert at a Lao food gathering in Luang Prabang in 2019, where chefs from all over brought local dishes and treats to share. One chef offered this rare dessert, and it stayed with me. Years later, a friend mentioned it while I was visiting her in Laos, and the memory came rushing back. That moment pushed me to revisit and recreate it.
What is activated charcoal?
Activated charcoal is a form of carbon made by burning natural materials like coconut husks, wood, or bamboo. It's known for its highly porous structure, which allows it to trap toxins, chemicals, and gases. Because of this, it's widely used in medicine, water filtration, beauty products, and even food.
The charcoal is created through a slow-burning process, and then it’s “activated” by exposing it to high heat—usually with steam or certain chemicals. This activation step opens up thousands of tiny pores on the surface, increasing its ability to absorb substances.
In food, small amounts of activated charcoal are generally safe. It’s sometimes used to help with mild food poisoning or accidental overdose by binding to toxins and preventing the body from absorbing them. However, when consumed in small quantities—like in black-colored desserts or drinks—it typically just passes through the body without any major effects.
*Please check with your doctor before taking activated charcoal, as it can interfere with how your body absorbs certain medications.
What is limestone paste?
Limestone paste is often used in a lot of Lao and Southeast Asian cooking.
Ingredients Needed for khanom piek boun | Lao Blackened Rice Cake
white limestone paste. Source of food grade calcium hydroxide where it helps firm up rice dishes.
Burnt coconut husk (or activated charcoal powder). This is what gives the dessert its natural black color. The husk must be burned properly to avoid releasing harmful toxins. If you want to skip the process of burning it yourself, you can use food-grade activated charcoal powder as a safer, ready-made alternative.
coconut milk*. Buy premade coconut milk, but if you want the best flavor, try making your own coconut milk with the directions in the recipe below.
tapioca flour. Part of the mixture to make it bouncy.
jasmine rice flour. Helps soften the dessert so its not just bouncy.
corn starch. helps smooth out the dessert.
salt.
sugar.
Step By Step Instructions
Make the activated charcoal
If you're making your own activated charcoal, start with clean, pesticide-free coconut husk. Always burn it outdoors or in a well-ventilated area. The burn should be controlled—low and slow—using a low flame or hot coals to ensure the husk carbonizes fully without turning to ash. When done properly, it should become a dry, brittle black powder that can be ground and sifted for use. For a safer and easier option, you can also use food-grade activated charcoal that’s ready to go.
Make the limestone water
I'm using red limestone paste here, but if you have access to white limestone paste, use that—it's the preferred type for cooking. Both have similar properties. To prepare it, place the limestone paste into a large jar and add the measured amount of water. Stir until the paste is fully dissolved. Let the mixture sit undisturbed for at least 1 hour and 30 minutes, allowing the sediment to settle at the bottom and the water to become clear. Carefully pour the clear water into a separate measuring cup—this is what you’ll use in the recipe. Discard the sediment left at the bottom.
Make homemade coconut milk
If you've never tried homemade coconut milk, it will completely change how you see this ingredient—it adds a richness and depth that elevates any dish.
Start by choosing an older coconut (the brown, mature kind). Use the dull side of a heavy knife to crack it open. Hold the coconut over a bowl to catch the water, then rotate and tap firmly until it splits. Gently open it and set the coconut water aside.
Next, steam the whole coconut for about 10 minutes. This softens the flesh and makes it easier to separate from the shell. Once it’s cool enough to handle, use a butter knife to carefully pry the flesh away from the shell.
Cut the coconut flesh into small pieces and process it in a food processor until finely ground. Transfer the ground coconut to a large bowl, add warm water, and mix well—squeezing and pressing to extract the milk.
Finally, strain the mixture through a sieve or cheesecloth, squeezing out as much milk as possible. That’s your fresh coconut milk—ready to use!
Mix the Flour
Now that all your ingredients are prepped, start by mixing the liquids with the charcoal powder until you get a smooth gray liquid.
In a large bowl, combine all the dry ingredients. Pour in the gray liquid and whisk until fully combined.
Transfer the mixture to a large nonstick pot and cook over high heat, stirring constantly, for about 20 minutes, or until the mixture becomes smooth and thick.
Pour in the mold and cool
Pour the mixture into a silicone pan and let it cool for 1 hour at room temperature. Use a silicone spatula to scrape all of the mixture out of the pot.
Once it has fully cooled and set, gently remove it from the mold and place it onto a cutting board. Cut into 2-inch cubes, then plate the cubes and top them with freshly shredded coconut before serving.
More Lao Recipes
Lao Blackened Rice Cake
Desserts are usually known for their bright, playful colors—but this Lao treat, khanom piek boun, goes in the opposite direction. Its striking black hue comes from the charred husk of coconut, giving it a bold, smoky appearance. Despite its dark color, the dessert is rich and sweet thanks to fresh coconut milk. The rice mixture is cooked, then left to set into a jello-like consistency, and each piece is topped with freshly grated coconut to add a light, refreshing finish.
Ingredients
Instructions
- To make slaked lime water, crush the limestone in a large bowl, adding a small amount of water to help break it down. Once fully mixed, pour in the remaining water and let the mixture sit for 1½ hours. Carefully pour the clear water into another bowl, leaving the sediment behind.
- For the burnt coconut husk, remove the husk from the coconut and place it in a fire-safe bowl. Light it on fire and allow it to burn completely until it turns into charcoal. Once cooled, crush it into a fine powder.
- In a blender, combine 4 cups of the slaked lime water with the charcoal powder and blend until well mixed. Strain through a sieve into a large bowl, then add the coconut milk and whisk until smooth.
- In a separate large mixing bowl, whisk together the tapioca flour, jasmine rice flour, cornstarch, salt, and sugar. Pour in the blackened limestone coconut water and mix until evenly combined.
- Transfer the mixture to a large nonstick pot and cook over high heat, stirring constantly for 20 minutes until smooth. Pour the cooked mixture into a cake pan and let it set for about an hour.
- Once firm, cut into 2-inch cubes, garnish with fresh coconut meat, and serve.
Notes
How to make fresh coconut milk
330g coconut meat (about 1 coconut)
4 cups warm water
Crack the coconut in half and drain the water. Steam the coconut in a rice steamer for 10 minutes. Use a butter knife to put in between the meat and shell all the way around until the meat pops out. Use a peeler to remove the dark outside layer of the shell. Cut the coconut in 1 inch pieces and then put in a food processor until it becomes fine like snow. Place the coconut in a Vitamix blender and add the measured water and blend for 1 minute. Place through a sieve and chill until ready to use.
Sabaidee, I’m Saeng!
I’m a personal chef who specializes in Lao food. Here at Saeng’s Kitchen, you’ll find all your favorite traditional Lao foods and also some new twists to Lao style dishes.