Make the pulled pork: pre-heat your oven to 350 degrees F (175 C).
Wipe down and dry your pork shoulder or pork butt. Wash your hands.
In a small bowl add your salt, smoked paprika and black pepper. Mix well. This is your rub.
Cover and rub your pork fully with all your rub. Make sure no parts of the pork are unseasoned.
In a Dutch oven or large oven safe pot (with lid), add your fully seasoned pork.
Pour 1 cup of apple cider vinegar into the Dutch oven or pot, around the pork.
Add a lid or cover to your oven safe pot and add it to the pre-heated oven.
Cook for 3 hours with the cover on the pot. If you don't have a cover, you can cover the pot with aluminum foil.
Once 3 hours are over, remove the cover/lid for the pot and cook for an additional 30 minutes.
Remove pork from the pot (don't discard any liquid left in the pot just yet), place it on a cutting board and allow meat to rest for 45 minutes to 1 hour and then pull meat from the bone and use two forks to separate it.
You might want to chop the pork a bit if your pieces are large. This will give it a good consistency for stuffing inside of buns.
Make the hoisin barbecue sauce: add olive oil to a small sauce pan over medium-high heat. Once the oil is shimmering, add garlic and cook it for 1 minute.
After a minute, add and stir in hoisin sauce, rice vinegar, sherry, soy sauce, ketchup, oyster sauce and water. Stir everything to combine well.
Simmer the sauce for 20 minutes stirring occasionally.
After 20 minutes, the sauce should have thickened up. Add sesame oil, stir well and remove the sauce from the heat.
Allow the sauce to cool and store in the fridge for up to two weeks.
Make the dough: in a large bowl or the bowl of your mixer, weigh out and add your all-purpose flour, salt, potato flour and instant yeast and stir to combine all your dry ingredients making sure there are no clumps.
Weigh the rest of your ingredients and add them to the bowl.
If using a stand mixer, knead for 8 minutes on medium speed. If you are kneading by hand, you will need about 15 minutes of kneading after all the ingredients are incorporated together.
The dough will be a bit sticky.
Place your dough in a lightly oiled bowl and cover. Let dough rise in a warm place for 1 to 1.5 hours. The dough should be doubled in size.
Remove dough from bowl to a lightly oiled counter and divide into 8 pieces. I like to weigh my buns at this point to keep them all fairly consistently sized, and I usually get 8 buns that are all between 85 and 90 grams each. Roll each portion of dough into a ball and let rest while you prepare the pork.
Shape and stuff the pork buns:
Add about 1 cup to 1 and 1/2 cups of pulled and chopped pork to a bowl. Spoon 4 to 6 tablespoons of hoisin sauce on top and toss the meat with the sauce. If it isn't sauced enough to your liking, add a little more. Add 3 tablespoons of sliced scallions (if using) to the pork and sauce and stir to combine.
Roll out the 8 dough balls, one at a time until you have a flat round of dough about 5 inches in diameter.
Spoon 2 tablespoons of pork and sauce and green onion into the center of each flattened dough disk.
Fold and pinch the sides of the dough over the top of the meat. Fold up all edges until you have a somewhat tight pouch. Flip the pouch of dough over, placing the pinched seam on the bottom and the smooth side on top.
Once you are finished rolling and stuffing all 8 portions of dough, place each stuffed dough on a parchment-lined sheet pan. Cover with greased plastic wrap or another inverted sheet pan and allow the dough to rest and rise for another 30 to 45 minutes.
Preheat your oven to 350 degrees F (176 C).
Add an egg and one tablespoon of water to a bowl and whisk until it's very combined. Paint this egg wash on top of each bun.
Bake the buns for 20 to 22 minutes or until they are shiny and caramel brown.
Allow the buns to cool for a few minutes before consuming. If you have extra buns, you can store them in the fridge for up to a week. Or in the freezer for up to 5 months. See the notes below for reheating procedures.
If you have leftover buns, the fully cooked, stuffed buns can be refrigerated for up to a week and they can be reheated in a 350-degree F (176 C) oven for 10-15 minutes.
You can also freeze these fully baked buns for up to five months. You can warm them by fully thawing and reheating them in a 350-degree F (176 C) oven for 10 to 15 minutes.
You should have extra pork after forming and baking all of these buns. You can freeze this for up to 5 months. When you're ready to eat it, fully thaw it out and warm it in the microwave, oven or a pan and it'll be just as good as when it was freshly cooked.