Place block of tofu on a paper towel lined plate and top with a heavy pan. Let tofu drain for 15-20 minutes, until it releases about a ½ cup of liquid.
Once tofu has released it's liquid, cut tofu into ½ inch cubes. Set aside.
Place dried mushrooms in enough boiling water to cover mushrooms and allow mushrooms to soak for 20-30 minutes or until they are soft and mushrooms are fully rehydrated. Drain and slice. Set aside.
Slice pork tenderloin into thin strip and then into matchstick sized pieces.
In a small dish, whisk together 1 tablespoon soy sauce, 1 teaspoon cornstarch, and 1 teaspoon sesame oil. Add sliced pork.
Stir to coat sliced pork with soy/sesame/cornstarch marinade. Set aside to marinate for 20-30 minutes.
In a small dish, combine 3 tablespoons water with 3 tablespoons cornstarch. Set aside.
In another small bowl, combine egg, ½ teaspoon cornstarch and 1 teaspoon water. Beat egg to combine. Set aside.
In another small bowl, combine 5 tablespoons black vinegar, 2 tablespoons Shaoxing sherry, 2 tablespoons rice wine vinegar, 2 teaspoons chili oil, 1 teaspoon pepper, and 3 tablespoons soy sauce. Stir to combine ingredients and set aside.
In a large stockpot bring chicken broth to a boil over medium high heat.
Stir in sliced bamboo shoots and sliced mushrooms.
Simmer for about 5 minutes, until mushrooms and bamboo shoots are tender.
Add marinated pork to the pot and stir to separate pieces.
Stir in tofu and continue to simmer soup until pork it cooked all the way through, about 5 minutes.
Stir in reserved cornstarch/water mixture and simmer until soup thickens.
Add vinegar/sherry/soy/pepper mixture and stir to combine. Bring soup to a simmer.
Once soup is hot, remove from heat and using a spoon, drizzle egg/cornstarch mixture into the soup using a cirular motion. Allow soup to sit for 1 minute before returning soup back to the heat source.
Stir soup gently to break up ribbons of egg and ensure egg is cooked through.
Serve soup topped with sliced scallions or chives.