For the belly of the beast: Add hoisin sauce, honey, sriracha and rice vinegar to a mixing bowl. Stir well. Reserve half for honey sriracha sauce and half for cooking liquid.
Rinse pork belly under cold water and pat completely dry. Scrape skin with a knife. Add pork belly to a vacuum bag and cover with cooking liquid. Seal bag and cook in a water bath at 155 degrees F for 24 hours.
Remove pork from water bath and let cool to room temp.
Preheat oven to 450 degrees F.
Once cooled, open bag and pour liquid into a saucepan. Reduce liquid to a glaze on medium heat, 5 to 10 minutes. Slice pork belly and cover with glaze in a roasting pan. Roast until glaze becomes tacky, 5 to 10 minutes.
For the bun daddy bun: Combine water, sugar and yeast in a stand mixer. Stir well and wait for foam to form, about 5 minutes.
Mix flour and baking powder together in a separate bowl and stir until mixed well.
Add 6 tablespoons oil to the yeast mixture, then add and combine the dry ingredients. Turn the mixer on low speed to incorporate everything, then mix on medium speed until a smooth dough ball has formed, 10 to 15 minutes. Remove dough from mixing bowl and oil the sides of the bowl. Place the dough back in the bowl, cover with plastic wrap and set in warm place to proof until dough has doubled in size, 1 to 2 hours.
Knead dough for 2 to 3 minutes, removing any air bubbles. Portion dough out to
roughly 2-ounce balls. Let dough proof again, loosely covered, for about 10 minutes.
Flatten dough balls with your palm and roll out to 1/4-inch-thick discs. Drop 1 to 2 drops of oil on the inside of a dough disc, fold in half and place in a bamboo steamer. Repeat with the remaining dough.
Steam buns for 12 minutes. Remove from heat, then add one slice of pork belly to a bun, followed by 4 to 6 cucumber slices, green onions, honey sriracha sauce and sesame seeds. Repeat with remaining ingredients. (Save remaining buns for another use.)
This recipe was provided by a chef, restaurant or culinary professional. It has not been tested for home use.