To make the infused water: In a bowl, combine the scallions and ginger. Pour the warm water over them, then gently squeeze and mix to release their flavor. Remove and discard the scallions and ginger.
To make the wonton filling: In a large bowl, mix the ground pork with the salt until fully absorbed. Add the white pepper, soy sauce, oyster sauce, Shaoxing wine, and cornstarch. Gradually pour in the infused water in two additions, mixing well after each addition until the liquid is completely absorbed. Stir in the chopped scallions until evenly combined.
To wrap the wontons: Brush water around the edges of a wonton wrapper. Place about 1 teaspoon of filling in the center. Fold one corner over to the opposite corner to form a triangle, then press the edges firmly to seal. Repeat with the remaining wrappers.
To make the soup: In a pot over high heat, bring the chicken stock to a boil. Season with the salt, soy sauce, sesame oil, and white pepper. Reduce the heat to low to keep the broth hot while you cook the wontons.
To blanch the Shanghai bok choy: Bring a pot of water to a boil over high heat. Add the Shanghai bok choy and blanch for about 30 seconds, until bright green and tender-crisp. Remove and set aside.
To cook the wontons: Bring the water back to a boil and gently add the wontons. Stir gently to prevent them from sticking. Cook for about 2 minutes, then pour in 1 cup of room-temperature water. Return the water to a boil and cook for another 2 minutes, or until the wrappers are translucent and the filling is fully cooked through.
To serve: Divide the cooked wontons among serving bowls. Ladle the hot broth over the top, then add the blanched Shanghai bok choy. Serve immediately.