I'm going to start off by saying I've never tried these. I came across the recipe on a Hong Kong blog that features videos of chefs preparing traditional dishes. I mentioned the recipe on facebook, and several friends asked me to translate it. This? Is the result.
Translated from here. (There is a recipe written down in Chinese, and a video in Cantonese.)
Kam Sa Lai Wong Yuht Beng (Custard and crushed yolk moon cakes)
Makes 8 55g. mooncakes
84 grams mooncake syrup (you can find recipes on Google - a syrup of sugar, water and lemon juice)
24 grams canola oil
600 grams flour
12 ml. (2 1/2 tsp.) alkaline water (found at asian grocers)
In a bowl, combine flour, oil, syrup and alkaline water. Mix it with your hand, covered in a plastic glove if you don't like getting messy. This will make a glossy, slightly oozy ball of dough. Cover the bowl with plastic wrap and refrigerate overnight.
75 grams flour
20 grams cornstarch
20 grams custard powder (or instant vanilla pudding)
160 grams sugar
20 grams glutinous rice flour
80 grams powdered milk
a few tbsp. of each: evaporated milk, sweetened condensed milk, coconut milk
100 grams butter
12 grams salted egg yolks, cooked and diced.
In a bowl, combine the cornstarch, flour, glutinous rice flour, custard powder, powdered milk and sugar. Stir until well mixed.
Stir in the 6 raw eggs and then the three kinds of milk. Mix well, and then steam the entire mixture for 30 minutes.
After 30 minutes, add the butter on top of the mixture and stir to combine, then mix in the crushed cooked, salted egg yolks.
Pull out your prepared "skin" dough and roll it into a log. Now roll your filling into a log. Cut your skin dough into 15 gram lumps, and your filling dough into 40 gram lumps.
Pick up one lump of skin dough, roll it into a ball, and then carefully squash it into a flat circle. Place your balled up lump of filling in the center and carefully use the skin to encase the filling.
Follow the directions on your mold to shape your moon cake, then place on a foil lined cookie sheet.
Spritz your sheet of shaped moon cakes with water, and then bake at 180 C. (350 F.) for 3 minutes. Remove from the oven and brush each cake with an egg wash, then bake another 7 minutes at 160 C. (325 F.) or until golden brown.
Allow to rest overnight.