Place the pork bones and skin in a pot and add enough cold water to cover. Bring to a boil, then immediately remove from heat, drain, and rinse off the bones, skin, and pot to remove impurities.
Place the bones and skin back in the pot along with the ginger, scallion, wine, and 4 cups of water. Bring to a boil. Reduce heat to a simmer, cover, and cook for 2 hours. The liquid should reduce to around 1 1/2 cups.
Remove from heat and allow to cool slightly. Strain the liquid into an 8x8 inch baking pan or wide bowl. Allow to cool to room temperature, then cover and refrigerate overnight.
In a large bowl, combine the bread and all-purpose flours. Make a well in the center and slowly add in the water and oil. Mix together with a wooden spoon, then knead to form a soft and smooth dough. If too crumbly, mix in a little more water. If too sticky, add a little more flour.
Wrap the dough in plastic or seal in a plastic bag, removing any excess air. Allow to rest at room temperature for 1-2 hours or refrigerate overnight, returning to room temperature before using.
In a small chopper or food processor, combine the ginger, scallions, rice wine, sesame oil, soy sauce, sugar, salt, and pepper. Blend until creamy.
In a medium bowl, combine the ginger scallion mixture and ground pork. Cover and set aside for 30 minutes or refrigerate until ready to use.
Remove the gelled stock from the refrigerate and slice into small 1/2 inch cubes.
Line steamer trays with parchment or cabbage leaves and set aside.
On a lightly floured surface, divide the dough in half.
Cover one half of the dough with a towel or plastic and roll the other into a rope about 10 inches long. Divide the rope into 8 equal pieces, covering with a towel.
Roll one piece into a ball and flatten into a circle. Gently roll out the edges, keeping the center slightly thicker. Try to get the edges thin enough to become translucent. Add 2-3 cubes of stock and about 1 tablespoon of the pork filling to the center of the circle, keeping 1/2-3/4 inch of the edge clear. Pleat the edges over the filling and pinch the tops together to seal, twisting gently. Repeat with remaining wrappers and filling. Cover the assembled ones with a towel to keep them from drying out.
Place the prepared dumplings in the parchment-lined steamer about 3/4 inches apart and 1 inch away from the edge.
Steam over boiling water at medium heat until the dumplings have puffed and become translucent, about 8 minutes.
Remove the steamer tray and place over a serving plate. Serve the Xiao Long Bao hot with the ginger vinegar dipping sauce, chopsticks, and a soup spoon.
Divide the vinegar among individual dipping bowls. Top each with julienned ginger.