Bring the vegetable stock and 2 cups water to a simmer in a large saucepan. Stir in the tofu, bean paste and ginger until well incorporated and bring to a gentle simmer.
Add the bok choy and fish fillets and cook until the fish is opaque and the bok choy is crisp-tender and bright green, 3 to 4 minutes. Season with white pepper and serve garnished with a generous sprinkling of the cilantro and a few Cordycep mushrooms, if using.
Cordycep mushrooms are a rare dried Chinese mushroom with a nutty, earthy, woodsy flavor; known for its positive effects on the immune system, lungs, and mental capacity. They can be ordered online and found in Chinese herb shops. Finely chopped dried Chanterelle mushrooms can be substituted as a garnish for the broth, if desired.