In a large pot, bring the chicken or vegetable broth to a boil.
Add sliced mushrooms and bamboo shoots to the broth.
Reduce heat and let simmer for 5 minutes.
Stir in the cubed tofu and green onions.
Mix soy sauce, rice vinegar, and white pepper; add to the pot.
Pour in the cornstarch mixture to thicken the soup.
Allow the soup to cook for another 2-3 minutes.
Stir in the beaten egg for a silky texture.
Taste and adjust seasoning if necessary.
Serve hot, garnished with fresh cilantro.