Turn onto a floured surface; knead until smooth and elastic, 10-12 minutes. Place dough in a greased bowl, turning once to grease top. Cover and let rise in a warm place until doubled, 40-60 minutes.

Meanwhile, in a large bowl, combine all filling ingredients. Refrigerate until use.

Punch down dough; lightly knead to remove any large air bubbles. Divide dough into 14 pieces. Roll each piece into an oval, about 1/4-in. thin.

Place oval in your palm, place a spoonful of pork filling in center. Pleat edges of dough until sealed; pinch top to seal. Repeat with remaining ingredients.

In a Dutch oven, place a steamer basket over 1 in. water. Line basket with cabbage or squares of parchment the size of the buns. In batches, place 4 buns in basket. Bring water to a boil. Reduce heat to maintain a simmer; steam buns, covered, until a thermometer reads 165°, 18-20 minutes. Carefully remove lid to avoid dripping condensation onto buns. If desired, serve with black vinegar or chili crisp oil.