In separate bowls, soak the dried lily flowers, wood ears, and shiitake mushrooms in 1 cup of hot water each for 1 hour, until hydrated. Reserve the shiitake mushroom soaking water.
Trim the tough ends off the lily flowers and cut them in half. Roughly chop the wood ears, and thinly slice the shiitake mushrooms. Cut the spiced tofu into thin 2 inch-long slices. Cut the tofu into ¼ inch thick pieces, also about 2 inches long.
Add the stock and strained mushroom soaking water to a large soup pot, and bring to a boil. Add the salt, sugar, dried chili pepper (if using), white pepper, dark soy sauce, light soy sauce, and sesame oil.
Next, add the lily flowers, wood ears, shiitake mushrooms, and bamboo shoots. Bring the soup to a simmer, and stir in the spiced tofu, firm tofu, and vinegar.
Combine the cornstarch with ¼ cup water to make a slurry. Ensure it’s well-combined, as the cornstarch tends to settle to the bottom of the bowl.
Bring the mixture to a simmer and use your soup ladle to stir the soup in a steady circular motion to make a whirlpool while slowly drizzling in the cornstarch slurry. This prevents the cornstarch from clumping. Simmer for another 30 seconds to thicken. (You can make/add more cornstarch slurry if you like your soup thicker, but don’t go overboard!)
Taste the soup and adjust seasonings to your preference. Add more white pepper if you like it spicier. You can also add more vinegar, soy sauce, or salt.
With the soup simmering/bubbling lightly, stir the soup in a circular motion once again. Slowly pour the beaten egg into the soup in a thin stream. When the egg is cooked, add the scallions, and serve!