1. For the wontons: Bring a large pot of salted water to a boil. Add bok choy, and cook until bright green, about 2 minutes. Drain, and let cool slightly. Press to remove excess liquid. Roll bok choy in a clean kitchen towel, and squeeze to remove any remaining liquid. Transfer to a food processor, and coarsely chop. Add pork and ginger, and pulse until mixture forms a coarse puree. Transfer to a bowl, and stir in soy sauce, wine, sugar, 1/4 teaspoon salt, and the pepper.

2. Place 1 wonton wrapper on a work surface. Spoon 1 tablespoon filling onto center of bottom half of wrapper. Lightly moisten edge of wrapper with a finger dipped in water. Fold top edge over filling to form a rectangle, gently pressing around the filling to squeeze out any air and seal the edges. With folded edge facing you, gently pull the 2 corners of the folded edge together to meet, pinching to seal with a dab of water. Flip up the sealed edge like the brim of a hat. Place wonton on a parchment-lined baking sheet, and cover loosely with a clean kitchen towel. Repeat. (Wontons can be frozen in a single layer on a baking sheet for 1 hour, then transferred to airtight containers and frozen for 2 weeks.)

3. For the soup: Thinly slice 2 scallions, and reserve. Gently crush remaining 6 scallions with a chef's knife, and place in a stockpot along with chicken, ginger, peppercorns, drained mushrooms, and the cold water. Bring to a boil, and skim foam from top. Add wine, reduce heat, and simmer very gently for 2 1/2 hours.

4. Strain mixture through a fine sieve lined with cheesecloth, reserving mushrooms and discarding remaining solids. Rinse mushrooms, and reserve. Let broth cool completely. Skim fat from surface. (Broth can be refrigerated in an airtight container for up to 5 days or frozen for up to 1 month.)

5. Add mushrooms and soy sauce to broth, and bring to a simmer. Season with salt to taste. Reduce heat to low, and cover to keep hot.

6. Bring a large pot of water to a boil. Add half of the wontons. As soon as wontons rise to the surface, add 1 cup cold water to pot. When wontons return to surface, remove with a slotted spoon, and place in the hot broth. Repeat with remaining wontons.

7. To serve, place 3 wontons in each bowl, and ladle soup over top. Sprinkle with reserved scallions.