If using dried wood ear mushrooms, place them in a bowl with hot water and rehydrate for 20-30 minutes until soft. Drain, rinse, remove any hard stems, and thinly slice.

Prepare all other ingredients: cube tofu, julienne bamboo shoots, and thinly shred pork or chicken (if using). Beat the eggs in a small bowl and set aside.

In another small bowl, whisk together the cornstarch and cold water until no lumps remain. This is your cornstarch slurry; set aside.

Pour the chicken or vegetable broth into a large pot or Dutch oven and bring to a simmer over medium-high heat. Add the light soy sauce, dark soy sauce (if using), rice vinegar, white pepper, and sugar. Stir well to combine.

Add the shredded pork or chicken (if using), rehydrated mushrooms, and julienned bamboo shoots to the simmering broth. Cook for 2-3 minutes, ensuring the meat is cooked through if applicable.

Add the cubed tofu to the pot and gently stir. Allow the soup to return to a gentle simmer.

Give the cornstarch slurry a quick re-whisk, then slowly pour it into the simmering soup in a thin stream, stirring constantly. Continue to stir until the soup thickens to your desired consistency. It should be slightly viscous.

Once thickened, slowly drizzle the beaten eggs into the soup in a thin stream while gently stirring in one direction (clockwise or counter-clockwise). This will create delicate egg ribbons. Stop stirring once all the egg is added and cook for about 30 seconds to set the egg.

Remove the pot from the heat. Stir in the sesame oil and chili oil. Taste and adjust seasonings as needed, adding more vinegar for tang, white pepper for heat, or soy sauce for saltiness.

Ladle the hot and sour soup into bowls. Garnish generously with sliced green onions before serving.