Custard Bun Recipe
For the bun:
1 tablespoon granulated sugar
¼ cup warm water (105°F)
2 ¼ teaspoon active dry yeast
4 cups all-purpose flour
2 tablespoon lard or shortening
½ cup granulated sugar
1 cup whole milk, warm (105°F)
1 tablespoon vegetable oil
1 tablespoon baking powder mixed with 1 ½ tablespoon water
For the filling:
1/4 teaspoon salt
1/2 cup sugar
About 1/2 cup cornstarch
1/2 cup coconut milk (can replace with normal milk)
2 tablespoons sweetened condensed milk
2 tablespoons unsalted butter, cut into 3 or 4 pieces
2 large egg yolks
1/2 to 1 teaspoon vanilla extract
For the bun
Dissolve sugar in warm water, sprinkle yeast over; let stand 2-3 minutes, and then stir to mix well. Let set until it starts to foam, 10 minutes. Sift flour and make well in the center. Whisk together the lard/ shortening, sugar, yeast mixture, and milk. The fat will not completely dissolve into the liquid. Combine liquid mixture with the flour; gradually incorporate the flour with the liquid to make dough. Knead the dough for 10 minutes (or leave it with your stand mixer and dough hook and mix for 5 minutes. Do not go over a 2 on a stand mixer when kneading dough), sprinkling with flour as necessary. Use the oil to grease the outside of the dough; cover and let rest in warm area 1 ½ hours or until double in size.
Punch dough down and flatten out to about ¾ inch thick. Spread the baking powder mixture evenly on the dough (this acts as a stabilizer). Roll dough up and knead about 10 minutes, or until smooth and satiny. The dough should be firmer than regular white bread dough. Cover and let rest 30 minutes.
Divide the dough into four equal parts. Roll one part by hand to form a rope approximately 9 inches long and 1¼ inch in diameter. Mark into 6 equal parts, 1 ½ inch long. Holding the dough with one hand, grip at the first mark with the thumb and index finger of the other hand and tear away briskly to break off a small dough piece. Continue breaking until you have 8 pieces.
Flatten each piece of dough with your palm. Using a rolling pin, roll each into a round disk, making quarter turn with each roll. Roll to leave the center thick; thinner edges are easier to pleat.
For the filling:
In a saucepan, whisk together the salt, custard powder, sugar, and cornstarch. Whisk in the coconut milk and condensed milk. Heat over medium heat, stir until smooth. Add the butter and continue stirring until the butter has melted. Keep stirring for about 6 minutes, until the mixture has thickens. As the mixture stiffens there may be lumps -> just stir more vigorously to get a smooth texture.
When the mixture is thick enough to stick to the whisk and form a soft peak, move the pan off the heat and whisk in the egg yolks. Put the pan to back on the stove and keep whisking to ensure that the yolks are well incorporated. Continue vigorously stirring for 1 to 2 minutes more, until the mixture thickens to the point where it cleans the sides of the pan and easily comes together as one smooth mass. If you have ever made dough for cream puffs, this is very similar. Stir in the vanilla, then take the pan off the heat. Stir it occasionally for a few minutes to quickly cool it.
At the end, stir the mixture off the heat for a minute and taste it. Make any changes you like at this point, as I suggest above. When you’re satisfied, transfer the filling to a bowl, spreading it out. After the filling has cooled, form it into balls (8 equal portions).
Assembling & cooking
Gather the edges by first pleating counterclockwise. Place the bun seam side down on a parchment paper. Let buns rest, covered for at least 30 minutes. Steam on high heat for 10 minutes.