Mix all the ingredients for seasonings, except for the flour, in the bowl. Set aside. Preheat your wok or skillet over high heat. Add in the oil. Add onions and ginger and saute until fragrant and soft, about 3 minutes. Add the BBQ pork (or uncooked chicken meat if that' what you are using, and cook until they turn opaque in color). Pour in the seasonings and red yeast rice powder (if using) and stir to mix. Sprinkle in the flour. The pork mixture will start to thicken and glue together. Have a taste and add more sugar if needed. It should be more sweet than savory. Turn off the heat and let it completely cool before wrapping
Once you have the basic steamed buns dough , divide the dough into 12 equal pieces. Lightly flour your work surface. Work with one dough at a time and cover the rest. Flatten the dough with your palm and then use a rolling pin to roll it out to form a circle about 4-5 inches, with a slightly thicker middle part. This is to support the weight of the filling. Don't roll the dough too thin. If you roll the dough too thin, the filling might make the steamed buns "wrinkle" later when you steam
FOR ROUND SHAPE: Place about 1 to 2 Tbsp of char siu filling in the middle and gather the edge to enclose into a round ball and place the seam side down. Cup the dough with both palms and move the dough in a circular motion to shape it taller. This part is important so your steamed buns come out tall instead of spreading to the side after steaming
Place on a piece of parchment paper. Lightly dab the surface of the bun with some milk using your finger to smooth the surface. Loosely cover with a clean cloth to prevent drying. Work with another dough and do the same
IF YOU WANT TO PLEAT SOME PATTERNS: Place the char siu filling in the middle. Create a fold around the edge and then pinch to seal. Cup the dough with both palms and move the dough in a circular motion to shape it taller. This part is important so your steamed buns come out tall instead of spreading to the side after steaming
Place on a piece of parchment paper. You don't need to dab the surface with milk if you have patterns. Loosely cover with a saran wrapper to prevent drying. Work with another dough and do the same
Let the shaped buns proof until about 50% double its original size. They don't have to double in size. This may take about 15 minutes, but please don't go by the time, just observe to make sure the buns have puffed up to half its original size and feel lighter, before steaming or the buns will be tough. Don't overproof them as well.
Most likely your steamer won't be able to accommodate steaming all buns at one go. You may need to steam in 2-3 batches, which means, the rest of the batches will sit longer and continue to proof while waiting for the steamer. Not good for the buns! Here's what you can do: Make sure the cover them with plastic wrap and then place them in the refrigerator to slow down the yeast activity or halt it all together until they are ready to be steamed
Bring the water in a steamer to a boil. Wrap the lid with a cloth. This will prevent water dripping from the lid creating burn spots. Place some of the buns on the steamer. Lower the heat to MEDIUM. Close the lid and leave about 1/4-inch of gap to let some steam escapes. Steam on MEDIUM heat for about 15 minutes. Turn off the heat and wait for 5 minutes and then remove steamed buns from the steamer to cooling rack. This will prevent the bottom from getting wet and soggy.
If you make extra and plan to store them, once the steamed buns have cooled down, place them on a baking sheet not touching each other and put them inside the freezer for 1 hour then transfer to a freezer bag
They can be reheated in the steamer without thawing. Steam over high heat for 5 minutes
If you don't have BBQ pork on hand, you can also use about 500 grams of uncooked chicken meat (thighs would be best if possible) or other meat or meatless protein of your choice. Cut into small pieces and cook as per recipe instruction