Because some like it extra hot, this Hot and Sour Soup packs heat from three different ingredients. Slideshow: More Asian Soup Recipes
In a small bowl, cover the lily buds with boiling water and let stand until softened, about 10 minutes. In another small bowl, cover the dried wood ear mushrooms with boiling water and let stand until softened, about 20 to 30 minutes. Rinse and coarsely chop.
In a large pot, heat the oil over moderately high heat. Add the garlic, scallions, ginger, chili flakes and pork and cook, stirring to break up the meat, until no pink remains, about 3 to 5 minutes. Add the stock and bring to a simmer. Measure out 1/4 cup of the stock and set aside in a small bowl. Add the tofu, lily buds, mushrooms, bamboo shoots, vinegar, soy sauce, sesame oil, sriracha, pepper and sugar to the pot and return the soup to a simmer. Using a circular motion, drizzle in the eggs and stir the soup gently until the eggs are cooked, about 30 seconds. Stir the cornstarch into the reserved 1/4 cup of stock and then drizzle the mixture into the soup, stirring gently until slightly thickened, about 3 to 4 minutes.
Taste and add more of the vinegar and soy sauce if desired. Divide into bowls and sprinkle each with a pinch of the crushed red pepper and a drizzle of the chili oil. Serve with additional chili oil.
This soup can be made the day before.
Lily buds, wood ear mushrooms, and Chinese black vinegar are available at Asian grocery stores.