If using, cut parchment paper into circles using the steamer basket as a tracing guide for getting the right size. (Alternatively, you can use unbleached paper coffee filters - I’ve done this and it works great.)
Combine warm water, milk, sugar, and yeast in a small bowl and let it activate for about 5 minutes.
Add dry ingredients to mixer bowl, slowly add yeast mixture, and mix on medium speed until rough dough ball forms; turn the mixer to the lowest setting.
While kneading with a dough hook, add oil slowly and allow the mixer to knead for another five minutes.
Remove the dough hook and cover the bowl with a towel. Allow it to rest until it is doubled in size. (Anywhere from half an hour to two hours, depending on the environment.)
Cover the work surface with a Silpat mat after the dough has doubled, and turn it out so you can punch it down gently to roll it out to about 1/4 inch thick.
Bring a pot of water to boiling while you complete the next step. (Make sure it is big enough to place the steamer on top without the bottom touching the water's surface.)
Cut out the bao buns using a 3 to 3.5 -inch circle cutter or large glass. (You should get between 12-16 buns depending on the thickness and size of your cutting tool.)
Prepare Pork Belly
Cut cold pork belly into one-inch cubes.
Mix dry rub ingredients in a small bowl.
Toss cubes in dry rub and set aside (or refrigerate) while you prepare the bao buns, sauce, and garnish.
Prepare Sauce
Add all sauce ingredients to a small saucepan and simmer on medium-low heat until the consistency of a glaze.
Assembly
Assemble by pulling apart bao bun, stuff with pork belly, drizzle with BBQ Sauce, then top with garnish of your choice.
Video
Notes
Gluten-Free Option: Works beautifully with Bob's Red Mill 1 to 1 gluten-free baking blendSugar-Free Option: Tastes just as good with Swerve Erythritol brown sugar substitute