Soak the dried mushrooms in the hot water for 30 minutes. Lift them out, squeeze them dry, trim off the stems and slice the caps thin. Strain the soaking liquid through a fine sieve and keep it.

Toss the pork with 1 tsp soy sauce and 1 tsp cornstarch.

Bring the stock, the mushroom soaking liquid and the ginger to a simmer in a large pot. Add the pork, stirring to separate the pieces, and cook for 2 minutes.

Add the mushrooms and bamboo shoots and simmer for 5 minutes. Add the tofu, the 3 tbsp soy sauce and the sugar and simmer for 2 minutes.

Stir the cornstarch and water mixture, then pour it in slowly while stirring. Simmer for 1 to 2 minutes, until the soup thickens and turns glossy.

Lower the heat so the soup barely moves. Drizzle in the beaten eggs in a thin stream, stirring once gently in one direction, and let the ribbons set for 30 seconds.

Turn off the heat. Stir in the vinegar, white pepper and sesame oil. Taste, and add more vinegar or pepper if you like. Serve topped with the scallions and chili oil.