In a large stock pot, boil 3 quarts of water. Place one piece of ginger inside the chicken's cavity. Add the salt, the rest of the ginger, and the chicken to the pot (breast side up). Let it simmer for 20 minutes, then turn the chicken upside down (breast side down) and simmer for another 20 minutes. Plate the chicken, then set aside.
Add the fish sauce, sherry, bok choy, and green onions to the pot. Bring to a boil, then simmer for 1 minute. Remove from the heat and serve.
When the chicken is cool enough to work with, slice and serve with the dipping sauce (recipe below), rice, and a bowl of soup with bok choy.
For the dipping sauce:
Whisk together all the ingredients, then serve with the chicken.
Recipe by Sprig and Flours at http://www.sprigandflours.com/chinese-chicken-soup-with-bok-choy/