Cut the pork into thin threads. Bring some water to a boil in a pot and blanch the pork in it for 2 minutes. Drain the meat and set it aside.
Soak the mushrooms in warm water for 20 minutes, then drain them and squeeze out any excess liquid. Discard the stems and finely shred the caps.
Soak the noodles for 5 minutes in warm water, then drain them. Cut them into 5-inch lengths and set them aside.
Drain the bean curd and shred it into thin strips.
Beat the eggs and sesame oil together in a small bowl.
Bring the chicken stock to a simmer in a large pot. Add the prepared pork, mushrooms, noodles and bean curd together with the sugar, vinegar, white pepper and dark soy sauce. Simmer for 3 minutes, then thicken it with the cornstarch mixture. Simmer for 2 minutes with the heat as low as possible.
Next, pour the beaten egg mixture into the soup in a steady stream, and pull the egg into strands with a fork or chopsticks. Stir in the scallions, fresh cilantro, sesame oil and chili oil. Pour the soup into a large tureen or individual bowls and serve at once.