Combine pork skin (2 lb), chicken feet (½ lb) (if using), ginger (4 slices)ginger (1 tbsp), scallions (2 stalks)scallions (2 tbsp), and water (8 cups)water (¾ cups) in a large pot.

Bring to a boil, then reduce heat and simmer for 3-4 hours, or until the broth is rich and flavorful.

Strain the broth through a fine-mesh sieve, discarding the solids. Let cool slightly, then refrigerate until completely solid.

In a bowl, combine ground pork (450 g), soy sauce (2 tbsp), Shaoxing wine (1 tbsp), sesame oil (1 tsp), ginger (4 slices)ginger (1 tbsp), scallions (2 stalks)scallions (2 tbsp), white pepper (¼ tsp), and salt (½ tsp).

Mix well until the filling is smooth and well combined.

Cut the solidified broth into small cubes and gently fold into the pork filling.

Cover the filling and refrigerate for at least 30 minutes to allow the flavors to meld.

In a large bowl, combine flour and warm water (8 cups)water (¾ cups). Knead until a smooth, elastic dough forms.

Cover the dough and let it rest for at least 30 minutes.

Divide the dough into small portions (about 15g each).

Roll each portion into a thin circle (about 3-4 inches in diameter), making the center slightly thicker than the edges.

Place a spoonful of the pork filling in the center of each wrapper.

Pleat the edges of the wrapper to create a small pouch, leaving a small opening at the top. Twist the top to seal.

Place the dumplings in a bamboo steamer lined with parchment paper or cabbage leaves.

Steam over high heat for 12-15 minutes, or until the dumplings are cooked through and the skin is translucent.

Serve immediately with black vinegar and ginger (4 slices)ginger (1 tbsp) slices.