Cut bamboo shoots into thin strips and then into fine slices.
To reconstitute the fungus (black or cloud ear), soak in warm water for 20 minutes.
Rinse, and cut into thin pieces. (If substituting Chinese dried mushrooms, soak to soften, then cut off the stems and cut into thin strips. If using fresh mushrooms, wipe clean with a damp cloth and slice.)
To reconstitute the dried lily buds, soak in hot water for 20 minutes or until softened. Cut off the hard ends.
Bring the water to a boil. When it is boiling, add the bamboo shoots, fungus or mushrooms, and the lily buds. Stir.
Add the tofu. Bring back to a boil and add the marinated pork.
Stir in the salt, sugar, soy sauce and vinegar and sesame oil.
Test the broth and adjust the taste if desired. (If using chicken broth, you may want to add a bit more rice vinegar).
Mix the cornstarch and water. Slowly pour the cornstarch mixture into the soup, stirring it while it is being added.
Let the broth come back to a boil. As soon as it is boiling, remove the broth from the stove.
Slowly drop in the beaten egg, stirring in one direction at the same time.
Add the green onion and the white pepper to taste. Drizzle with chili oil if desired. Serve hot.
(Hot and Sour Soup can be prepared ahead of time and frozen. When making the soup, leave out the tofu. When ready to serve, thaw, add the tofu and bring to boiling. When the soup is boiling, add the egg.)