Making Steamed Buns with Mung Bean Filling: A Thai Dessert Guide

What are steamed buns with mung bean filling?

Steamed buns with mung bean filling are a beloved Thai dessert and snack. They consist of a soft, fluffy white bun made from a simple yeast dough, wrapped around a sweet, smooth paste of golden mung beans. The buns are steamed until puffed and tender, then served warm. Their appearance is distinctive: a round, cloud-like bun with a smooth, slightly shiny surface, often with a swirl or sealed top hiding the golden filling. The filling is fragrant with pandan leaf or a hint of coconut, while the bun itself has a mild, yeasty aroma. The texture contrast is delightful—the bun is light and airy, and the filling is creamy and dense.

In Thailand, these buns are known as salapao sai tua (filled bun with bean) or more specifically salapao sai tua thong if using golden mung beans. They are commonly found at morning markets, from street carts, or in dim sum restaurants with Thai influences. They are usually eaten as a breakfast item, a snack with tea or coffee, or as a dessert after a meal.

Preparing the dried mung beans for the filling

Dried mung beans are small, round, green beans that turn soft and golden when cooked. They are the key to a smooth, sweet filling that is less oily than red bean or lotus seed pastes. To prepare them, you need to soak, cook, and mash them into a paste.

Step-by-step mung bean paste filling

1. Soak the beans: Rinse 1 cup (200 g) of dried split mung beans (preferably hulled and split, often labeled "moong dal") in several changes of water. Soak in plenty of water for at least 2 hours, or overnight. This reduces cooking time and makes them easier to digest. Hulled split mung beans are yellow; if you have whole green mung beans, you will need to remove the skins after cooking, which is more laborious.
2. Steam the beans: Drain the soaked beans and place them in a heatproof dish or a muslin-lined steamer basket. Steam over boiling water for 15–20 minutes until very tender—a bean should squash easily between your fingers. Alternatively, simmer in water, but steaming keeps them drier, so the filling is easier to thicken.
3. Mash with flavorings: While the beans are still hot, transfer to a bowl and mash thoroughly with a fork or potato masher until smooth. For an ultra-smooth texture, pass through a sieve or blend with a little water. Add 1/2 cup (100 g) sugar (palm sugar for caramel notes, or white sugar for a cleaner sweetness), a pinch of salt, and optional flavorings: 2–3 pandan leaves tied in a knot (remove after cooking) or 1/4 teaspoon pandan paste, or 2–3 tablespoons of thick coconut cream for richness. Mix well.
4. Cook the paste: Heat a nonstick pan over medium-low heat. Add the mashed bean mixture and cook, stirring constantly, until it thickens and pulls away from the sides of the pan, about 10–15 minutes. The paste should be thick enough to hold its shape when rolled into a ball but still moist. Let cool completely. Divide into 12 equal portions (about 25–30 g each) and roll into balls.

Substitutions: If you cannot find mung beans, you can use yellow split peas (soak longer and cook until very soft) or canned sweetened mung bean paste (adjust sugar). The flavor will be slightly different but still pleasant. Avoid red bean paste as it is much darker and stronger in taste.

Making the steamed bun dough

The bun dough is a basic yeast dough enriched with a little oil and sometimes milk or coconut milk. Unlike Western bread, it contains less yeast and is steamed rather than baked, resulting in a very white, tender crumb.

Recipe for 12 small buns

• 2 cups (250 g) all-purpose flour, plus extra for dusting
• 2 tablespoons sugar
• 1 teaspoon instant yeast
• 1/2 teaspoon baking powder (optional, for extra fluffiness)
• 1/2 cup (120 ml) warm water or milk (about 110°F/43°C)
• 2 tablespoons neutral oil or melted shortening
• Pinch of salt

Method

1. In a large bowl, whisk together flour, sugar, yeast, baking powder, and salt. Make a well in the center.
2. Pour in warm water and oil. Mix with a spoon until a shaggy dough forms.
3. Turn out onto a lightly floured surface and knead for 8–10 minutes until smooth and elastic. The dough should be soft but not sticky.
4. Place in a lightly oiled bowl, cover with a damp cloth or plastic wrap, and let rise in a warm place until doubled in size, about 1–1.5 hours.

Proofing is essential: After shaping, the buns must proof again before steaming. This second rise ensures they are light and airy. If the dough is not properly proofed, the buns will be dense and heavy.

Assembling and shaping the buns

Once the dough has doubled, punch it down and divide into 12 small pieces (about 25 g each). Roll each piece into a ball, then flatten into a disc about 8 cm (3 inches) in diameter, with the edges thinner than the center. Place a ball of mung bean filling in the center. Gather the edges up around the filling and pinch to seal tightly. Roll the filled bun gently between your palms to make a smooth ball. Place it seam-side down on a small square of parchment paper (to prevent sticking). Repeat with remaining dough and filling.

Arrange the buns in a steamer basket, leaving at least 3 cm (1 inch) between them because they will expand. Cover with a lid and let proof for 20–30 minutes, until they look slightly puffy and feel soft. The buns should not double in size but should increase by about 50%.

Steaming the buns

Steaming is what gives these buns their characteristic soft, moist texture. Use a bamboo steamer for a subtle woody aroma, or a metal steamer—both work well. The steamer must be tall enough to allow the buns to rise without touching the lid.

How to steam

1. Fill a wok or large pot with about 2 inches (5 cm) of water and bring to a rolling boil.
2. Place the steamer basket(s) over the boiling water, ensuring the water does not touch the buns. Reduce heat to medium-high so the water simmers steadily.
3. Steam the buns for 12–15 minutes. Do not lift the lid during the first 10 minutes, or the buns may collapse.
4. After steaming, turn off the heat and let the buns rest in the steamer for 5 minutes before removing the lid. This prevents sudden temperature change from wrinkling the surface.
5. Serve warm. The buns are best eaten the same day but can be stored in an airtight container in the refrigerator for up to 2 days and resteamed for 3–5 minutes.

Visual cue: Properly steamed buns are snowy white, puffy, and spring back when lightly pressed. If they are yellowish and dense, the dough was over-proofed or the water boiled too vigorously, causing uneven heat.

Flavor variations and serving suggestions

While the classic filling is plain sweet mung bean, you can enhance it:

• Coconut mung bean filling: Add 2–3 tablespoons of thick coconut cream to the paste and use coconut milk instead of water in the dough for a richer taste.
• Pandan mung bean filling: Add pandan juice or paste to the filling; the green flecks and fragrance are very Thai. The buns themselves can also be tinted pale green with pandan juice.
• Salted egg yolk center: For a savory-sweet contrast, press a small piece of salted egg yolk into the center of the filling ball before wrapping. This is a popular dim sum style.

Serve the buns with hot Thai tea, coffee, or as part of a dim sum spread. They are also lovely with a drizzle of sweetened condensed milk or a dusting of toasted sesame seeds.

Comparison: steamed buns vs. baked buns vs. other filled buns

This table helps you distinguish these similar buns. The mung bean bun is the most delicate in flavor and often has a whiter, softer crumb than baked counterparts.

Tips for success

• Use hulled split mung beans: They cook quickly and yield a smooth golden paste without skin removal. Whole mung beans have green skins that must be rubbed off after cooking, which is tedious.
• Do not overfill: Too much filling makes wrapping difficult and may cause the buns to burst during steaming. Use about 25 g filling for a 25 g dough ball.
• Keep the buns covered: While shaping, cover unused dough balls to prevent drying. Dry dough will crack when wrapped.
• Steam with a cloth under the lid: If using a metal steamer, tie a clean kitchen towel around the lid to absorb condensation and prevent water droplets from falling onto the buns, which would create pockmarks.
• Test for doneness: A cooked bun will sound hollow when tapped on the bottom. If it feels heavy, steam for another 2–3 minutes.

Conclusion

Making steamed buns with mung bean filling at home is a rewarding project that introduces you to the gentle, fragrant side of Thai dessert making. The process—from soaking dried beans to steaming the finished buns—is a sensory lesson in transformation: hard green beans become a golden, creamy paste; a simple flour dough puffs into a cloud-like bun. With the instructions above, you can recreate a beloved Thai treat that is as beautiful as it is delicious.