Soak mushrooms and lily flowers in boiling hot water for 20 minutes. Drain and reserve soaking liquid.
In a large pot, combine soaking liquid and chicken stock. Bring to a boil and season with salt. Simmer 5 minutes, add tofu, exotic mushrooms and bok choy. Slowly add egg to soup, stirring gently. Then add pork or chicken. Cover and cook about 5 minutes.
Stir a little of the hot stock into cornstarch paste and add this mixture to the soup. Cook another 2 minutes.
Stir in sesame oil, vinegar, and chili paste or black pepper. Sprinkle with scallions and cilantro, serve immediately