To braise the pork belly, heat the vegetable oil in a large saute pan until it is nearly smoking.
Pat the pork belly dry with paper towels, and quickly sear both sides of the pork belly until you have a nice golden-brown crust on the exterior of the pork belly.
Remove the pork belly from the saute pan and allow it to rest on a plate.
Deglaze the saute pan using a few tablespoons of water, and combine this deglazing liquid with the chicken stock.
Cut the pork belly into 1.5” cubes.
In a soup pot, combine the chicken stock, seared pork belly, soy sauce, brown sugar, garlic, ginger, star anise, and green onions.
Bring to a gentle simmer and reduce the heat to low.
Braise for about 3 or 4 hours, or until the pork belly is completely fork-tender.
While the pork belly is braising, prepare the pickled onions.
For the pickled onions, combine the rice vinegar, white granulated sugar, red pepper flakes, and Kosher salt in a bowl, stirring until the sugar has dissolved.
Add the thinly sliced onions and let them pickle for at least an hour, stirring occasionally and making sure that the onions are submerged in the liquid.
Set the pickled onions aside for later.
For the cabbage slaw, combine the shredded cabbage and julienned carrots in a large bowl.
In a separate smaller bowl, whisk together the mayonnaise, sour cream, hoisin sauce, rice vinegar, Kosher salt, and freshly-ground pepper.
Pour this dressing mixture over the cabbage and carrots, tossing everything to combine.
Once the pork belly is cooked and completely tender, let it cool down in the braising liquid.
When the pork belly is cool enough to handle, pull the chunks of pork using your fingers and break it down into the consistency of pulled pork.
To assemble the bao buns, steam the buns according to the package instructions until they are soft and warm.
Open each bun and layer in the braised pork belly, pickled onions, sweet and sour pickles, and Hoisin cabbage slaw.
Top each bun with fresh cilantro leaves and freshly-squeezed lime juice.
Serve the Pork Belly Bao Buns while everything is still warm.