Direct answer: Molten liu sha bao need a frozen, high-fat salted egg yolk filling inside a soft yeast dough. Cook and mash the yolks, blend them with butter, sugar and milk powder, freeze firm portions, then seal them without thin spots. Proof gently and steam over medium-high heat for 8 minutes so the buns cook before the center escapes.
Key takeaways
- Cook salted duck egg yolks before making the filling.
- Blend the yolks very smooth for an even molten center.
- Freeze individual filling balls until completely firm.
- Keep the wrapper thicker in the center and seal cleanly.
- Steam briefly and serve warm, when the filling flows best.
What is liu sha bao?
Liu sha bao are Cantonese steamed buns filled with a sweet-salty custard made from salted duck egg yolks. The name means “flowing sand bun,” describing the warm golden filling as it runs from a freshly opened bun. They differ from ordinary nai wong bao, whose egg custard is thicker and remains in place.
The flowing texture comes primarily from fat, not undercooked egg. Butter and coconut milk loosen the cooked yolks when warm, while milk powder adds dairy flavor and controls excess liquid. A cold filling and an even dough shell prevent leaks during proofing and steaming.
Ingredients for 10 buns
Salted egg filling
- 6 cooked salted duck egg yolks, about 90 g
- 6 tablespoons/85 g unsalted butter, softened
- 1/2 cup/60 g dry milk powder
- 1/3 cup/65 g fine sugar
- 3 tablespoons/45 ml full-fat coconut milk
- 1/4 teaspoon fine salt, only if needed
Steamed bun dough
- 2 1/2 cups/320 g low-protein or all-purpose flour
- 2 tablespoons/24 g sugar
- 1 1/2 teaspoons/5 g instant yeast
- 1 teaspoon/4 g baking powder
- 2/3 cup plus 1 tablespoon/175 ml lukewarm whole milk
- 1 tablespoon/15 ml neutral oil
Allow 45 minutes active work, 2 hours freezing, 1 to 1 1/2 hours proofing and 8 minutes steaming.
Step 1: cook the salted egg yolks
If using raw salted duck egg yolks, place them in a heatproof dish and steam over simmering water for 10 minutes, until fully cooked and crumbly. Cool completely. Packaged cooked yolks may be used according to the label.
Check the flavor before adding extra salt. Saltiness varies by brand and curing method. Do not use raw yolks directly in a filling intended to flow; the molten appearance must come from melted fat, not uncooked egg.
Step 2: make a smooth filling
Press the cooked yolks through a fine sieve or blend them until no hard pieces remain. Mix with softened butter, milk powder, sugar and coconut milk until glossy and uniform.
The mixture should resemble a thick paste at room temperature. If grainy, continue blending; if extremely loose, chill it for 15 minutes before portioning. Taste a small amount only after the yolks have been fully cooked.
Step 3: freeze individual portions
Divide filling into ten 28-to-30-g portions. Spoon them into a silicone mini-muffin mold or onto parchment, shape into compact balls and freeze for at least 2 hours.
They must be solid enough to handle without smearing. Frozen portions give the dough time to set during steaming before the butter melts. Keep them in the freezer until each wrapper is ready.
Step 4: mix the bun dough
Whisk flour, sugar, yeast and baking powder. Add lukewarm milk and oil, then stir until a rough dough forms. Knead for 8 to 10 minutes by hand, or 6 to 8 minutes in a mixer on low, until smooth.
The dough should feel soft but not sticky. If dry flour remains, add milk 1 teaspoon at a time. Avoid adding excess flour, which produces thick, dense buns and makes sealing harder.
Step 5: complete the first proof
Put the dough in a lightly oiled bowl, cover and proof at 75 to 80 F/24 to 27 C for 45 to 60 minutes, until about 1 1/2 times its original size.
It does not need to double. Overproofed dough can weaken around the heavy filling. Press with a floured fingertip; a slow partial spring-back means it is ready.
Step 6: divide and roll the wrappers
Gently press gas from the dough and divide into ten equal pieces, about 52 g each. Shape into balls, cover and rest 10 minutes.
Roll one piece into a 4 1/2-inch/11-cm circle. Make the edge about 1/8 inch/3 mm thick while leaving the center closer to 1/4 inch/6 mm. The thicker center protects the base from the liquid filling.
Step 7: fill and seal without leaks
Place one frozen filling portion in the center. Lift opposite edges, gather the dough above the filling and pinch every fold firmly together. Twist off excess dough only if the top becomes very thick.
Turn seam-side down and cup the bun gently into a round shape. Set it on a 3-inch/7.5-cm parchment square. Keep filling off the wrapper edge; butter on the seam prevents it from bonding.
Step 8: proof the shaped buns briefly
Arrange buns at least 2 inches/5 cm apart in steamers. Cover and proof for 20 to 30 minutes at room temperature. They should look slightly puffed, not doubled.
Meanwhile, bring water to a steady boil. Ensure the water level remains below the steamer and wrap a metal lid in a clean towel if condensation normally drips onto food.
Step 9: steam for a molten center
Set the steamer over boiling water and steam over medium-high heat for 8 minutes. Do not lift the lid. Turn off the heat, wait 2 minutes, then open the lid away from your face.
Serve after 3 to 5 minutes of cooling. The filling is extremely hot when first opened. Steam one test bun before the entire batch if your wrappers are thicker; add 1 to 2 minutes only when the dough remains raw.
How to control the filling texture
A warm filling should pour slowly. More butter or coconut milk loosens it but increases leak risk; milk powder thickens it. Adjust 1 teaspoon at a time, then chill and warm a spoonful to judge the texture.
If filling stays firm, the fat ratio is too low or the bun cooled too long. Reheat by steaming 4 to 5 minutes rather than extending the original steaming time.
Substitutions
Canned coconut milk
Shake it well and use the rich, full-fat liquid. Light coconut milk produces a less fluid filling.
No coconut milk
Use evaporated milk, beginning with 2 tablespoons. The flavor changes slightly, so adjust after testing a warmed spoonful.
All-purpose flour
It works well. Cake flour gives a softer, whiter bun but may need slightly less milk.
Unsalted chicken egg yolks
They do not reproduce the savory, sandy character of salted duck yolks. Use a standard custard-bun recipe instead of treating them as a direct substitute.
Common mistakes
The filling does not flow
Too much milk powder, too little fat or cooling caused it to set. Reheat the bun and adjust the next filling batch by small amounts.
The filling leaks into the steamer
The portion was soft, the wrapper had thin spots or the seam was greasy. Freeze fully, keep the center thick and pinch clean edges.
The buns wrinkle
They were overproofed, exposed to sudden temperature change or hit by lid condensation. Proof only until slightly puffy and rest 2 minutes before opening.
The dough is dense
Yeast was inactive, dough was too dry or proofing was insufficient. Use fresh yeast, lukewarm milk and visual proofing cues.
The filling tastes too salty
Salted yolks vary. Omit added salt and increase sugar by 1 tablespoon in the next batch rather than diluting with excess liquid.
Food safety and storage
Do not taste raw dough or uncooked yolks. Flour and eggs can contain harmful germs. Wash hands and utensils after raw egg contact, cook yolks before blending and steam the bun dough completely. Egg dishes should reach 160 F/71 C; check a test bun without touching the hot liquid center.
Refrigerate cooled buns within 2 hours and use within 3 to 4 days. Reheat by steaming 4 to 5 minutes. Freeze cooked cooled buns individually for up to 1 month, then steam from frozen for 8 to 10 minutes. Discard buns with damaged packaging, mold or off odors.
Related lessons
For another filled steamed dough, make steamed red bean buns. Our guide to collapsed or wrinkled bao explains proofing and condensation, while Cantonese egg tarts develop custard temperature control.
Recipes4Less cooking courses show wrapper thickness, filling consistency and sealing pressure visually, making these subtle texture cues easier for beginners to recognize.
FAQ
Are liu sha bao sweet or savory?
They are both: sugar and dairy make the custard sweet, while salted duck egg yolks provide savory depth.
Can I use a bamboo or metal steamer?
Either works. Prevent metal lids from dripping condensation and keep every bun on parchment.
Can I freeze unsteamed buns?
Cooked buns are more reliable for beginners. Freezing raw yeast dough can change proofing and increase leak risk.
Why is the filling orange?
The color comes naturally from salted duck egg yolks. Its intensity varies; artificial coloring is unnecessary.
Can I make the filling one day ahead?
Yes. Freeze the measured portions airtight overnight and fill the buns directly from frozen.
Conclusion
Molten liu sha bao rely on cooked smooth yolks, enough fat, frozen filling and an evenly sealed wrapper. Proof modestly, steam briefly and cool just enough to eat safely. The result is soft bao with a warm sweet-salty center that flows without raw egg.