1 tablespoon Vegetable or Canola Oil
3/4 -1 small Onion, chopped
1/2 cup Dried Wood Ear Mushroom (nấm mèo đen), soaked until soft, rinsed and chopped
1 bunch Vermicelli Bean Threads (bún tàu), soaked until soft, chopped
1 1/2 tablespoons Oyster Sauce
2 Vietnamese Sausages (lạp xưởng), each cut into 20 round slices
5 boiled eggs, each cut into 4 pieces
20 Paper Circles using paper or parchment paper
Pour a bag of flour into a mixing bowl.
In a separate bowl, mix sugar, lemon and milk until sugar dissolved. The purpose of using lime juice is to make the bun white. Keep about 2 tablespoons of the milk mixture on a side. Pour the remainder into the flour bowl. Mix the ingredients well with a wooden spoon in preparation for kneading. Keep stirring it with a spoon until all the ingredients are combined, then you're ready to start kneading. You should use the palms and heels of your hands to push forward on the dough. If the dough is dried, add a a teaspoon of milk mixture at a time to soften the dough. Add a teaspoon of flour to achieve a nice soft dough if the dough is too tacky. How much liquid all depends upon your brand of flour, how old it is, and the temperature and humidly of the room.
After about 5 minutes of kneading the dough, test it by touching the dough with your clean and dry hand. The dough should be soft and should not stick to your hands. Add oil and knead it for another minute.
Cover the mixing bowl with a cloth or towel. Leave it somewhere that is not cold (I usually warm the oven up for a few minutes then turn the oven off and leave it in the oven) and let it rise for about half an hour to 45 minutes. Divide dough into 20 balls. Cover dough with a towel to keep the surface of the dough from drying out.
While waiting for dough to rise, prepare the filling.
Mix all the ingredients except sausages and eggs. Divide the meat into 20 balls.
Roll out each dough ball but not too thin.
Place a meat ball in the center of dough. Add 2 pieces of sausages and 1 piece of egg.
Hold the edges of dough over the filling with your thumb and index finger and start folding it into layers while using the other hand's thumb push down the filling. At the end, twist all the layers to make it stick together. Put the completed bun on a piece of circle paper.
Boil 3/4 of water in a bottom layer of steamer at high heat. Arrange buns on the other layers of steamer. Leave space between each bun to make room for it to rise and expand. Steam the buns when water starts boiling. After 20 minutes, the buns should be puffed up and they are ready to eat.