Thread necromancy
per vm's request. This is how I made the soup; if you want the full-dress version you have to read Mr. Bittman's excellent book. As usual, amounts and times are flaky.
Mark Bittman's Hot and Sour Soup, Abridged
1 tsp cornstarch
1 tsp soy sauce
1 tsp dark sesame oil
1 tsp Chinese cooking wine, sherry or sake (I think this is optional)
1 boneless, skinless chicken breast, either partially thawed or partially frozen, sliced extremely thinly against the grain
1.5 cans low-sodium chicken broth
1 clove garlic, minced
1" piece ginger, peeled and minced
Some dried shiitake mushrooms -- like 6 -- soaked, drained and sliced thinly
2 more tbsps soy sauce
1/4 c rice wine vinegar (right) or white wine vinegar (wrong, but works)
Lots of freshly-ground black pepper
2 more tbsps cornstarch
1 egg, lightly beaten
Chopped scallion for garnish
Whisk first 4 ingredients together in a small bowl and set chicken to marinate in mixture. Put broth, ginger and garlic together in a pot and bring to a simmer. Add mushrooms. Simmer for 5 minutes. Bring to a boil and add chicken, stirring so it doesn't stick to itself, and cook till done, about 3 minutes. Simmer for another 5 minutes. Season with remaining soy sauce, vinegar and pepper. Whisk remaining cornstarch together with a small amount of water and stir it into soup. After soup thickens, trickle egg in there in a very thin stream, stirring gently. Correct seasoning. Garnish with scallion and eat immediately; this doesn't reheat well.
There's all kinds of other shit that's supposed to go in there, like lily buds and wood-ear mushrooms and tofu, and you can use pork or sirloin instead of chicken. But again, for that you need the book.
Enjoy!