Making Steamed Mung Bean Cake for Thai Cooking

Steamed mung bean cake is a traditional Thai dessert made from hulled mung beans that are soaked, ground into a smooth batter, sweetened, and steamed in small molds until set. The cake is soft, slightly chewy, and fragrant with coconut or pandan, often served as a snack or part of a dessert platter.

What Is Steamed Mung Bean Cake?

Steamed mung bean cake is a pale yellow or green cake with a tender, slightly bouncy texture. It is made primarily from hulled mung beans, which are split yellow mung beans with the green skin removed. The beans are soaked until soft, blended with coconut milk and sugar into a mung bean batter, and then steamed in small cups or cake molds. Unlike baked cakes, it has no crust and a moist, dense crumb that gently resists the bite.

The aroma is sweet and nutty from the mung beans, enriched by coconut milk, and often brightened with pandan leaf extract, which gives a floral, grassy note and a natural green color. In Thailand, this cake is known as khanom mo kaeng tua or variations like khanom tua paep, depending on the region and added flavors.

Essential Ingredients for Steamed Mung Bean Cake

Each ingredient contributes to the cake's flavor, texture, and appearance:

• Hulled mung beans: These split yellow beans are the base. They have a mild, slightly sweet, earthy flavor and become very soft when soaked and steamed. They provide the cake's body and protein.
• Coconut milk: Adds richness, moisture, and a creamy tropical aroma. Use full-fat coconut milk for a tender cake; light coconut milk will make it drier.
• Sugar: Palm sugar is traditional, giving a caramel-like depth and light brown color. White sugar can be substituted for a cleaner sweetness and paler cake.
• Pandan leaves or extract: Optional but common. Pandan lends a sweet, grassy fragrance and a natural green hue. The juice is extracted by blending leaves with water and straining.
• A pinch of salt: Balances the sweetness and enhances the nutty flavor of the beans.

For a simple steamed mung bean cake recipe, the ratio is roughly 1 cup of dried hulled mung beans to 1/2 cup coconut milk and 1/3 to 1/2 cup sugar, adjusted to taste. The batter should be thick but pourable, like pancake batter.

How to Prepare Dried Mung Beans for Steaming

Preparing the dried beans is the most important step for a smooth cake. Follow these steps:

1. Rinse: Measure 1 cup of hulled mung beans and rinse them in cold water until the water runs clear.
2. Soak: Submerge the beans in at least 3 cups of water for at least 4 hours, or overnight. The beans will double in size and soften. This shortens steaming time and makes blending easier.
3. Drain and rinse again: After soaking, drain the beans and rinse once more.
4. Blend into batter: Put the soaked beans in a blender with 1/2 cup coconut milk and blend until completely smooth. The mixture should have no visible bean particles. If it's too thick, add a little more coconut milk, 1 tablespoon at a time.
5. Sweeten and flavor: Pour the batter into a mixing bowl. Stir in the sugar, salt, and pandan extract if using. Mix well until the sugar dissolves.

If you don't have a blender, you can mash the soaked beans with a fork or potato masher, but the cake will have a coarser texture. A food processor also works well.

Steaming the Cake: Tools and Technique

Steaming is a gentle cooking method that sets the batter without drying it out. You will need a steamer pot or a wok with a steaming rack, and small heatproof cake molds. Thai cooks often use small ceramic cups, banana leaf cups, or silicone molds in flower or round shapes.

Step-by-step steaming:

1. Prepare the steamer: Fill the bottom of a steamer pot or wok with water, making sure the water level is below the steaming rack. Bring the water to a rolling boil.
2. Grease the molds: Lightly brush the inside of each mold with coconut oil or vegetable oil. This helps release the cake after steaming.
3. Fill the molds: Spoon the mung bean batter into the molds, filling each about 3/4 full to allow for slight expansion.
4. Arrange in steamer: Place the molds on the steaming rack, leaving a little space between them so steam can circulate.
5. Steam: Cover the steamer with a lid wrapped in a cloth to prevent water droplets from falling onto the cakes. Steam over medium heat for 15–20 minutes. The cakes are done when a toothpick inserted into the center comes out clean and the surface is firm and slightly glossy.
6. Cool and unmold: Remove the steamer from heat and let the cakes cool for 5 minutes. Run a thin knife around the edges and invert the molds onto a plate. Serve warm or at room temperature.

Comparison of common mold materials:

Flavor Variations and Serving Ideas

The basic steamed mung bean cake is versatile. Common variations include:

• Pandan version: Add 2–3 tablespoons of pandan juice for green color and aroma.
• Coconut topping: Before steaming, top each cake with a small spoonful of salted coconut cream for a savory-sweet contrast.
• Taro or pumpkin: Mix in steamed and mashed taro or pumpkin for different flavors and colors.

Serve the cakes as a snack with tea, or as part of a Thai dessert platter alongside fresh fruit and sticky rice. They are best eaten the day they are made but can be stored in an airtight container in the refrigerator for up to 2 days. Re-steam briefly to restore softness.

Common Mistakes and Troubleshooting

• Grainy texture: The beans were not soaked long enough or not blended thoroughly. Soak at least 4 hours and blend until fully smooth.
• Waterlogged cake: Steam condensed and dripped onto the cakes. Cover the steamer lid with a cloth or use a bamboo steamer.
• Too dense: The batter was too thick. Add a little more coconut milk to reach a pourable consistency.
• Sticking to mold: Grease the molds generously, especially if using metal or ceramic.

With practice, you can adjust sweetness and flavorings to suit your taste. Steamed mung bean cake is a delightful introduction to Thai sweets, showcasing the natural goodness of dried beans transformed by simple steaming.