To make the stock: In a large stockpot, combine the chicken, stock, peppercorns, ginger, onion, carrot, celery and bay leaf. Bring to a simmer over medium-high heat. Reduce the heat to low and continue to simmer the stock uncovered 30 minutes, skimming the froth from the top every now and then and discarding it.
Strain the stock into another large pot, discarding the bones and vegetables. Skim and discard the fat from the top of the stock with a large spoon. Depending on how aggressively your stock has cooked, it may have reduced somewhat. Taste the stock.
If it is a little salty, add water in 1/4 cup increments until a balance has been achieved.
To make the wontons: In a large bowl, combine the pork, 2 Tblsp of green onion, the wine, soy sauce, five-spice powder, and pepper. Mix thoroughly. To taste for seasoning, heat a small skillet and fry a tablespoon size patty until it's no longer pink inside. Taste and adjust seasoning as desired.
On a work surface, lay out about 6 wonton wrappers, keeping the remaining wrappers covered with plastic so they don't dry out. Moisten the edges with your fingertip dipped in water. Drop 1 Tblsp of the pork filling into the center of each wrapper and flatten it slightly, leaving a generous border. Press another wrapper on top, like ravioli. Press from the center out to the edges to remove any air from the wonton. Run your finger around the edges to seal.
Arrange the wontons on a parchment-lined sheet pan and refrigerate while you continue with the remaining wrappers and meat mixture. You may have some leftover filling.
You can make more wontons and freeze them up to 1 month or cook extra for large appetites.
Bring a large pot of water to a boil over medium-high heat. Add the wontons 6 at a time and cook for 4 minutes, stirring to keep them from sticking to the bottom of the pan. Remove the wontons from the pot and transfer them to a covered dish to keep warm. Repeat until all the wontons are cooked.
Ladle the stock into bowls and add 2 wontons to each serving. garnish with the chopped green onions. Serve hot.
The stock can be made up to 2 days in advance.