2) Put the tree ear and shiitake mushrooms in separate small bowls and pour over boiling water to cover. Set aside for about 30 minutes.
3) Meanwhile, put the stock, garlic and ginger in a large pan. Crush the white part of 1 spring onion with the side of a knife and add to the pan. Simmer, covered for 15 minutes.
4) Thinly slice the remaining spring onions and reserve. Remove the mushrooms from the water and discard the liquid. Squeeze out any excess moisture and thinly slice.
5) Remove the garlic, ginger and spring onion from the broth and discard. Add the mushrooms, soy sauce, balsamic vinegar, pepper and salt and bring to a simmer.
5)Whisk in the cornflour mixture, bring to a boil, and then simmer over medium heat for 5 minutes. Pour the egg into the soup and stir once to make delicate threads.
6) Stir in the sliced spring onions, sesame seed oil, tofu and pork. Return the stock to a simmer then remove the pan from the heat to prevent the meat from getting tough. Adjust the seasonings to taste. Serve immediately.