Shell and devein shrimp. Grind shrimp and pork in food processor until well-blended. Remove to bowl and add ginger, soy sauce, egg, sesame oil, sugar, sherry and minced green onion. Mix well.
Place about a teaspoon filling in the lower corner of won ton skin. Fold corner over and press edges to seal. Use egg yolk to bring side corners together to seal.
In Dutch oven, bring water to boil. With a slotted spoon, place won tons in water. Stir gently so that they do not stick to the bottom of the pan. Bring again to boil and add cold water. Let return to boiling again. Won tons are done when they float on the water. Remove to plate and discard water.
In pot, combine chicken broth, ginger, garlic, soy sauce, sesame oil, dry sherry, mirin and pepper. Bring to boil and add won tons. Add bok choy and green onion and cook until bok choy is parboiled. Remove from heat and serve immediately.
Add other vegetables as desired: Napa Cabbage, Snow Peas, Broccoli, Carrots, Bean Sprouts and Shitake Mushrooms, for example.