Preheat the oven to 300˚F.
Drizzle some oil into an ovenproof pot or Dutch oven set over medium-high heat and brown the pork in batches, sprinkling with salt and pepper and transferring it to a bowl or plate as you go.
Add the oranges and enough water to come halfway up the side of the pork, cover and braise for 3 hours, or until the meat is very tender.
Pull the meat apart with two forks, adding the hoisin sauce and green onion. (If there seems to be too much liquid, simmer on the stovetop until the liquid has reduced.)
Pinch off pieces of dough the size of a golf ball and roll or flatten each piece into a circle that’s about 1/4-inch thick.
Put a heaping spoonful of the pork onto each circle, then pull and fold the sides up over the filling, pinching and twisting the edges together to seal.
Place each ball seam-side down in paper muffin cups sprayed with nonstick spray.
Place them in a bamboo steamer basket and steam over an inch or two of boiling water for 12-15 minutes, until puffy and cooked through.
Scatter the buns with sesame seeds as soon as they’re done, and serve with fresh cilantro and lime wedges.