How to Make It
Set a fine sieve over a large bowl. In a medium saucepan, combine the clam broth, mushrooms, celery, fennel, kombu, and 4 cups of water; bring to a simmer. Cook over low heat for 1 hour. Strain the broth into the prepared bowl; discard the solids. Season the broth with salt, if needed, and keep warm.
Meanwhile, in a small bowl, cover the fermented black beans with 1 inch of water, and let soak for 20 minutes.
In a small skillet, heat the sunflower oil. Add the garlic and minced ginger, and cook over medium heat, stirring, until the garlic is golden brown, about 1 minute.
Drain the black beans, discarding the liquid. In a food processor, pulse the black beans, garlic mixture, smoked oysters, oyster sauce, and 2 tablespoons of water until smooth. Scrape the smoked oyster sauce into a small bowl.
In a large nonstick skillet, heat 1 tablespoon of the rice bran oil until shimmering. Season the fish with salt and pepper, and cook over moderately high heat until opaque throughout, about 4 minutes per side. Transfer to a heatproof platter.
In a small skillet, heat the peanut oil until very hot, about 1 minute. Immediately pour the oil over the fish.
Dollop the smoked oyster sauce in 4 shallow bowls. Set fish on top. Ladle the warm broth around the fish. In a medium bowl, toss the tatsoi with the lemon juice and remaining 1/2 teaspoon of rice bran oil, and season with salt. Scatter the tatsoi around the fish and garnish with the scallions and julienned ginger. Serve hot.