Mix cornstarch and water to form a slurry.
Heat char siu glaze in a saucepan on the stove.
When glaze comes to a bubble, slowly pour in the slurry while whisking continuously.
Keep whisking until glaze has thickened to BBQ sauce or honey-like consistency.
Toss chopped char siu with glaze and store in fridge until ready to make buns.
Make Chinese mantou dough according to recipe (see elsewhere in this post) through the first rise.
Divide risen dough into eight equal portions. Roll each portion out into a 3-4 inch circle.
Place about 2 tbsp of char siu filling in the center of each circle. Bring up the edges of the circle and fold or pinch together. See other videos for fancy folding technique.
Place each folded bao onto a 4 inch square of parchment paper. Then place all bao in your steamer, covered, to rise for another 20-30 minutes.
In the last 5-10 minutes of the second rise, prepare your steamer.
Place bao in whatever steaming contraption you use and cook for 15 minutes. Enjoy!