1. Put the mushrooms, tree ears and lily buds into separate bowls and cover with boiling water. Let stand 30 minutes.
2. Meanwhile, slice the tofu into strips (thick matchsticks), and set aside.
3. Combine the pork shreds with the dark soy sauce in a small bowl. In a different container, combine the light soy sauce, vinegar and salt.
4. Drain the black mushrooms, cut off the woody stems and discard, then slice the mushrooms thinly and put into a bowl. Drain and rinse the tree ears and add them to the mushrooms. Drain the lily buds, cut off the woody tips, cut each in half, then pull each half into shreds by hand; add to the mushrooms.
5. Heat the oil in a large pot. Add the pork and stir fry until it changes color. Add the tree ears, mushrooms, lily buds and bamboo shoots; cook, stirring, for 1 minute. Add the stock and bring to a boil. Stir in the vinegar mixture. Reduce heat to medium and cook for 1 minute, then add the tofu and cook for another minute.
6. Recombine the cornstarch and water and stir into the soup. Cook until the soup thickens and clears slightly. Swirl in the beaten eggs. Turn off heat and sprinkle with the pepper, drizzle in the sesame oil, garnish with green onion and cilantro and serve.