Cook chicken strips until they have an internal temperature of 170 degrees F (using a meat thermometer to test). Set aside. IMPORTANT: don't cook as much as you'd cook a chicken breast you might eat by itself: heating the soup will continue to cook the chicken, resulting in tough, overcooked chicken in your soup.
Dissolve tamarind paste by heating with an ounce of the chicken stock. (microwave is a good way to do this). Remove any seeds from melted paste, since they're inedible.
If using pickled radish, chop as finely as you can make it, since they're hard to chew.
Bring stock to boil. Add tamarind/stock mixture, soy sauce, chinkiang vinegar, pepper, bamboo shoots, mushrooms, radish, and chestnuts; SAVE LIQUID FROM BAMBOO SHOOTS & CHESTNUTS. Stir. Let cook for 3 minutes.
While cooking, in separate bowl combine cornstarch or flour and liquid from the previous step to make a slurry. Add slurry a little at a time and stir until thick (all slurry may not be necessary, so add as much as necessary for desired thickness).
Add eggs while stirring and cook for 30 seconds or until eggs are done. Add green onions and chicken.
Cut tofu into strips that are about 1/4" x 1/4" x however thick the tofu brick is.
Remove from heat. Add rice vinegar and tofu and blend thoroughly.