You've had hot and sour soup before...but have you ever made it?
This soup might have you buying ingredients you've never heard of - go with it. You'll make it and then you'll make it again and again and again.
Begin by emptying all the chicken stock in your soup pot. Add the stone, 2 cups of water, peppercorns, the onion (cut in half), green onions (all split down the center) and 3 of the ginger pieces. Bring to a boil and then simmer while preparing below.
Put the wood ears in a small bowl and cover with boiling water. Let stand for 30 minutes to reconstitute. Drain and rinse the wood ears; discard any hard clusters in the centers.
Heat the oil in a wok over medium-high flame. Add the ginger, chili paste, wood ears, bamboo shoots, and pork; cook and stir for 1 minute to infuse the flavor. Combine the soy sauce, vinegar, salt, pepper, and sugar in a small bowl, pour it into the wok and toss everything together - it should smell really fragrant.
Remove the stock from the heat and strain all solids (including the stone from the broth. Add the stock directly to the wok, bring the soup to a boil, and simmer for 10 minutes. Add the tofu and cook for 3 minutes.
Dissolve the cornstarch in the water and stir until smooth. Mix the slurry into the soup and continue to simmer until the soup thickens. Remove the soup from the heat and stir in 1 direction to get a current going, then stop stirring. Slowly pour in the beaten eggs in a steady stream and watch it spin around and feather in the broth (it should be cooked almost immediately.) Garnish the hot and sour soup with chopped green onions and cilantro before serving.