Recipe for Nǎi Huáng Xiàn (奶黄馅) - Custard Filling for Steamed Buns

Yield:

Time:

Place the yolks in a large bowl.
Separately, mix the sugar and corn starch together.
In a small saucepan, combine the milk, butter, and whole milk powder, and bring the mixture to a boil.
Whisk the sugar-starch with the yolks, then pour the hot milk mixture into egg mixture, making sure to whisk while pouring.
Bring the bowl over to a pan partially filled with water. Bring the pan to a simmer. Cook in a water bath, whisking continuously, until the custard thickens, about 5 minutes. Continue cooking for an additional 1-2 minutes.
Scrape the custard filling into a heatproof bowl, cover with a piece of plastic wrap, and steam for 30 minutes.
Remove from the steamer, place into a container with a lid, and refrigerate. Cool completely before using in baked goods and confections.

With most custards that have a sugar and a starch as a thickener, I like to mix the sugar and starch together before mixing it with the other ingredients. This helps prevent large pockets of uncooked starch from appearing in the mix.
Give the milk mixture a gentle stir to loosen up the milk powder.
I poured just an inch of water into a fry pan, placed a ring of foil in the pan, and rested the bowl on the foil to keep it from direct heat. You want the custard filling to be receiving the heat from the simmering water, but not so hot that you're curdling the mixture. Remember to keep stirring the mixture to prevent it from curdling and burning.
Use whatever steaming method works for your kitchen, as long as the custard liquid is covered before steaming (to prevent excess water from dripping in). I used a steamer insert (a flat, circular metal disc with feet) inside a pot, and nested a bowl of custard liquid on top of it.
This recipe makes roughly 16-18 custard buns, averaging about 30-35g per custard ball.

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