Ingredients  
Dough 
  • 80 ml (1/3 cup) warm water
  • 2¼ tsp (1 pkg) dry active yeast
  • ½ tsp sugar
  • 2½ cups unbleached all purpose flour
  • 2½ cups cake flour
  • 4 tbsp sugar
  • 2 tbsp butter or margarine, melted
  • 120 ml (½ cup) dairy or soy milk
  • 180 ml (¾ cup) water
  • 16 squares of parchment paper
Filling 
  • 230 gm (8 oz) prepared seitan, any style, drained and coarsely chopped
  • 1 tbsp vegetable oil
  • ½ tsp light sesame oil (ie untoasted) a drop or two of dark sesame oil maybe mixed in but it does have a very strong flavour.
  • ½ tsp salt
  • ½ tsp sugar
  • 1 tsp soy sauce
  • 1 tbsp hoisin sauce or mushroom soy sauce
  • 2 tbsp water
  • 1 tsp tapioca starch or corn starch
Method:  
Dough  
  1. In a 1 cup (240 ml) measuring cup, blend the water, yeast and sugar and let stand in a warm place until it foams up to the 1 cup mark, about 20 minutes.
  2. In a large mixing bowl combine the flours, sugar, and salt until well mixed.
  3. Add the melted margarine, yeast mixture, soy milk and water and knead until it becomes a soft, pliable dough.
  4. Place this in an oiled bowl and cover with a damp cloth.
  5. Let rise for 3 hours in a warm spot that is free of drafts.
Filling 
  1. Heat a large skillet or wok, and add the oil.
  2. Toss in the chopped seitan and cook for a minute or two.
  3. Add all the remaining ingredients except the last measurement of water and starch.
  4. Bring the seitan and sauce to a boil.
  5. In a small dish blend the last amount of water with the starch until it has no lumps.
  6. Add this to the seitan and sauce mixture and cook for one or two minutes until it has thickened.
  7. Remove from heat and allow to cool.
  8. Assemble the buns  
  9. After the dough has risen, remove it from the bowl and knead it three or four times.
  10. Break it up into 8 equally sized pieces.
  11. Working quickly, flatten each piece of dough out until it is about a handspan in diameter.
  12. Scoop a generous, heaping tbsp of the prepared filling into the center, then bring the edges of the dough circle up over it, and pinch it all tightly closed.
  13. Place the bun on one square of parchment and arrange on a cookie sheet or other large platter.
  14. Repeat these steps until all 8 buns are filled.
  15. Cover the buns with a damp cloth and let rise in a warm spot for about 20 minutes, then steam in a vegetable steamer or bamboo steamer for 25 minutes.
  16. At this point the buns can be eaten, or cooled and stored in an airtight container in the fridge for freezer for later re-steaming (just until hot) and consumption.
Source