Steam

Salted Egg Yolk Custard Buns (Lau Sa Bau)

by:
April 27, 2020
Photo by Julia Gartland. Prop Stylist: Sophie Strangio. Food Stylist: Samantha Seneviratne
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

  • Prep time 9 hours
  • Cook time 12 minutes
  • Makes 16 filled buns
Ingredients
  • 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
In This Recipe
Directions
  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.

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Coral Lee is an Associate Editor at Food52. Before this, she cooked food solely for photos. Before that, she cooked food solely for customers. And before that, she shot lasers at frescoes in Herculaneum and taught yoga. When she's not writing about or making food, she's thinking about it. Her Heritage Radio Network show, "Meant to be Eaten," explores cross-cultural exchange as afforded by food. You can follow her on Instagram @meanttobeeaten.