Place the dried mushrooms into a deep bowl and cover with hot water for 15 minute, or until rehydrated (they should double in size and be soft to the touch). Once rehydrated, slice the mushrooms into thin strips.
Press excess liquid out of the extra firm tofu either with a tofu press or by wrapping it in lint free kitchen towels and placing a flat heavy object on top for around 10 minutes. While waiting for these two steps, gather the rest of the ingredients. Cut the tofu into 1/2 inch cubes.
Into a large pot, add in the broth, grated ginger and white part of the scallions over medium high heat.
Add in the mushrooms, tofu, water chestnuts, bamboo shoots, soy sauce and sugar. Once it comes to a boil, reduce the heat down to a medium low and cover. Let it simmer for 8-10 minutes to let the flavours come together.
Mix together the corn starch and water to make slurry, ensuring there are no lumps. While stirring, slowly pour in the corn starch slurry. Continue to stir to thicken the soup (1-2 minutes)
Remove the pot from the stove and add in the green onions, chili bean paste (if using) vinegar, white pepper and sesame oil. Taste and add more rice vinegar, salt and pepper to taste.
Serve immediately and garnish with cilantro.
Find dried shiitake mushrooms and/or wood ear mushrooms at your local asian market
To make Guten-free: use tamari instead of soy sauces
Nutritional Information Disclaimer: Nutrition information is a rough estimate calculated on an online tool (Cronometer).