Salted Egg Yolk Custard Buns (Lau Sa Bau)

April 27, 2020
2 Ratings
Photo by Julia Gartland. Prop Stylist: Sophie Strangio. Food Stylist: Samantha Seneviratne
  • Prep time 9 hours
  • Cook time 12 minutes
  • Makes 16 filled buns
Author Notes

If you’ve been following along, you know I have a thing for salted eggs. As salt penetrates the yolks, it draws out water (concentrating the fat), and breaks proteins down into free glutamates (what our tongues detect as umami). Eggy, buttery, rich—cured egg yolks add a bottomless depth and savoriness to sweet treats that sweet treats never knew they needed.

Part one of my salted egg yolk love letter manifested as an upgraded pound cake, but it would be remiss to not acknowledge the most classic of vehicles: lou sa bao, or “leaking sand buns,” typically served at dim sum (in Cantonese, literally small, shared bites that “touch the heart”). Most of the fun of eating these steamed, downy buns is navigating the molten, salted custard that jets out upon first bite. Novices will get hot-pocket-mouth. Veterans know to bite then suck the lifeblood out of the unassuming buns.

The simple, yeasted dough comes together quickly in a stand mixer—and if you’ve made buttercream before, you can make this custard filling. (Peek here for a recipe for home-cured egg yolks.) The filling is modeled after Bird’s custard—an instant, tinned variety popular in the U.K. and resultantly H.K.—but not as cloying, courtesy of crunchy salt flakes. Don’t confuse milk powder (essentially milk devoid of water) with malted milk powder (milk powder mixed with malted grain). Though, in thinking about it now, if that’s all you have around, please do use it and report back with your findings. That sounds absolutely, positively delicious.

While I like to let the dough rest overnight in the fridge, if you absolutely, positively need to slurp these buns on the day of, simply let the dough rise at room temperature for an hour instead. If all you have is active dry yeast, no sweat—simply increase the amount by 125 percent: a heaping one and a half teaspoons (or five grams). The flavor of the dough will suffer slightly (not as sweet and yeasty), but let’s be real: The buns are mere vehicles for the filling anyway. —Coral Lee

What You'll Need
  • Dough
  • 2 1/3 cups (300 grams) all-purpose flour, plus more for dusting
  • 1/2 cup (60 grams) cornstarch
  • 1/2 teaspoon kosher salt
  • 1 1/4 teaspoons (4 grams) instant yeast
  • 3 tablespoons (38 grams) granulated sugar
  • 1/2 cup (120 grams) whole milk
  • 1/2 cup (120 grams) water, at room temperature
  • 1 tablespoon tablespoon neutral oil, such as grapeseed
  • Custard filling
  • 3 salted egg yolks (see Author Notes for recipe link)
  • 3 tablespoons unsalted butter, room temperature
  • 3/4 cup (90 grams) confectioners’ sugar
  • 3 tablespoons (24 grams) milk powder
  • 3 tablespoons (23 grams) cornstarch
  • 2 tablespoons (32 grams) evaporated milk
  • 1 1/2 teaspoons pure vanilla extract
  • 1 tablespoon flaky salt, such as Maldon
  1. Combine all of the dough ingredients in the bowl of a stand mixer fitted with a dough hook. Knead on medium-low speed until the dough looks smooth and elastic, 7 to 10 minutes. Lid the bowl with a large plate or damp towel, and let proof in the fridge for at least 8 hours and up to 24.
  2. Meanwhile, make the filling: Cook the salted yolks in a small pot of boiling water until hard-boiled, about 5 minutes. Use a slotted spoon to transfer the yolks to a stand mixer fitted with the paddle attachment and beat on medium speed until finely mashed. Add in the remaining filling ingredients and mix on medium until smooth and the texture of a fluffy buttercream, 3 to 5 minutes. Transfer filling to an airtight container, and freeze for at least 2 hours or up to overnight.
  3. The following day, scoop golf ball-sized balls (each weighing about 15 grams) of the frozen filling onto a baking sheet (you should get about 16), press a few flakes of salt onto each, and freeze until you’re ready to fill buns.
  4. Punch down the dough, and roll into a 1 1/2–inch thick rope on a lightly floured work surface. Divide the dough into 16 pieces (each weighing about 35 grams). Working with one piece at a time, turn the dough cut side up, and place a frozen ball of filling in the center. Pinch the dough around the filling, then flip the ball seam-side down. Roll around on the work surface to seal the seam. Place the filled bun onto a square of parchment, and set the parchment inside your steamer, giving each bun an inch or so of clearance. Repeat with all of the dough and filling. Lid the steamer, and let the buns rise once more, another 30 minutes. (If you have a mini steamer like me, simply let the buns rise, covered, on a sheet pan, and steam in batches.)
  5. When ready to cook, bring the water to a boil, and steam the buns for 7 minutes, or until puffed and cooked through. Remove the buns from the steamer, and let cool slightly before devouring.

See what other Food52ers are saying.

  • Kaila Yu
    Kaila Yu
  • Coral Lee
    Coral Lee
  • knitwitgirl
  • AllieBear

20 Reviews

knitwitgirl November 28, 2021
Could you please provide a variation of your recipe - a pineapple bun recipe with the salted egg custard filling? Thank you.
Coral L. November 29, 2021
Hi knitwitgirl! Our wonderful resident, Mandy Lee, has a recipe for bolo bao on her site:

You can use this recipe here for the filling, rolling it into the pre-proofed buns in the "To bake the pineapple buns" step.

Hope this helps!
AllieBear June 6, 2021
These turned out way better than I thought they would. I wish the recipe had a video to show what consistency the hard boiled salted egg yolks should look like and how to seal the buns. Pretty much all of my buns leaked, the filling didn't freeze up hard and made it difficult to seal the dough around it since it was so soft still. After steaming they tasted great, the dough for bun was so light and airy, it paired nicely with the sweet salty filling. I will give these another try and try to get them sealed better.
AllieBear June 6, 2021
Also, I only had malted milk powder instead of plain, and we all enjoyed the extra malty flavor it added. I thought it was going to be too malty since it was a lot of powder, but after it was cooked, the flavor was pretty subtle and nice.
Kaila Y. May 14, 2020
Why is it better to proof the dough overnight, instead of for 1 hour in a warm place?
Coral L. May 14, 2020
Hi Kaila! The overnight rest slows the yeast activity down, while allowing naturally present lactobacilli to produce acid (ie a more flavorful, complex-tasting dough). The 1 hour proof in a warm spot will leaven the dough just fine—it just may not be as deeply flavored.
Kaila Y. May 14, 2020
Thank you! I was planning on making this tomorrow
Kaila Y. May 15, 2020
Hi! So I purchased salted duck eggs from the Chinese market. Is there a different form of preparation for these? The yolks were soft but still solid. I tried two methods boiled and steaming. The boiled yolk disintegrated and the steamed yolks, 2 were good, and one kind of melted. Not sure what I did wrong!
Coral L. May 15, 2020
Hi! It sounds like the eggs you got are not as cured. Can you crumble them right out of the box? Or did the steamed yolk crumble better? If the latter, would just steam the yolks and for less time (maybe start checking for doneness around 2-3 minutes?).
Kaila Y. May 15, 2020
Thank you! Is it possible to freeze the buns for later after they've been formed and filled with the egg yolk filling?
diana May 12, 2020
I just finished making these. The cream filling is good, not too sweet. However in order to get 16 balls, I used my larger size melon baller. This is much smaller than the golf ball size they specify. The dough was terrific. I can see adding nutella or other fillings if you want something unique and don't have time to make the salted yolks.
Coral L. May 12, 2020
Yum, very into the nutella filling. Thanks for making these, Diana—and for the tip about the melon baller.
Grace May 9, 2020
Does this need to be done with a bamboo steamer or can I use a normal metal pot to steam it?
Coral L. May 9, 2020
Hi Grace! Metal pot is fine. Just make sure the buns are raised off the floor of the pot — they can grow soggy that way.
Grace May 9, 2020
Thank you so much!!
Grace May 9, 2020
The metal pot I have is a steamer. Does it need to be raised up from the metal steamer or is that okay?
Coral L. May 12, 2020
Ah! Sorry I missed this, Grace. A metal steamer should be fine—perhaps line each layer with a parchment round to help with moisture-control.
A May 9, 2020
Why dough for 16, filling for 10?
Coral L. May 9, 2020
Hi! Good question (and eye). I've adjusted the language—thanks for the catch!
A May 9, 2020
Thanks Coral!