1If using dried shiitake mushrooms, soak in the hot water until softened (takes about 15 mins). Slice the mushrooms into 1/8 inch strips, put mushroom soaking water into the pot. If you don't use dried shittake mushrooms, add about a coup of water to the soup to compensate for this mushroom infused water.
2In a separate bowl, mix together: all the sherry, 1 tablespoon sesame oil, 1 tablespoon soy sauce, 1 teaspoon cornstarch.
3Slice the pork against the grain into thin strips, place in the bowl with the sherry and other ingredients, mix together and set aside.
4Blend together remaining 1/3 cup cornstarch with cool water in a small bowl, set aside, but keep a spoon in the bowl (you'll probably need to re-stir at some point)
5Combine remaining 2 tablespoons soy sauce with vinegar, worcestershire, and white/black pepper in another bowl, and set that aside.
6Add stock to soup kettle with the mushroom infused water. Bring to a boil over medium heat, then reduce to simmer and add muishrooms and bamboo shoots, also water chestnuts if you're adding them. Bring to simmer and cook around 5 minutes.
7Stir in the tofu and pork- carefully so as not to break the tofu, cook for another 2-3 minutes.
8Recombine the cornstarch mixture and stir into soup until it thickens, about 1 minute
9stir in vinegar mixture, turn off heat.
10slowly drizzle beaten egg into the soup, using a swirling motion and trying to keep the egg strands thin. When the egg is completely poured in, gently stir but only for a few seconds. At this point the soup is done.
11Serve garnished with thinly chopped scallions, that are mixed with the remaining 1 tablespoon sesame oil.
12Serve immediately as possible, but the soup does alright if left on a very low heat. If you bring back to a boil it will thin out so avoid.