To make the won tons: combine the ground turkey, 1/3 cup of the water chestnuts (chopped fine) [save the rest for the soup], onions, soy sauce, salt, pepper, ginger, garlic and sherry. In a small bowl, beat the egg.
Place 1 won ton skin on countertop or other flat surface (cover remaining skins to keep pliable) Mound 1 teaspoon of the meat filling in one corner. Fold that corner over filling and roll to tuck point under. (see photo on won ton wraps/if available) Moisten the 2 side corners with egg and bring together, overlapping slightly. Pinch together firmly to seal. Repeat with remaining skins. Cover and refrigerate until ready to use.
To make the soup: In a large soup pot add the chicken broth and the water. Bring to a boil and add the chicken. Simmer for 20 minutes and add salt, soy sauce and and pepper. Add add mushrooms, celery, onion, left over water chestnuts and bok choy. Bring soup back to a boil and add the won tons. Simmer for 10 minutes. Add green onion on top and serve with white rice.
Note: This soup is "thick" with won tons. If you prefer to use less, you can freeze some of them on a baking sheet until firm and then transfer them to a plastic bag and return to freezer for another time. (Do not freeze them uncooked if you plan to deep fry them).