Make the fermented bean curd cured black sea bass: Place the fish filets on a clean surface and spread the fermented bean curd onto both sides. Cover in plastic wrap and refrigerate overnight. Wipe off the fermented bean curd and slice the fish into ¼-inch strips.
Make the gochujang cured Spanish mackerel: Place the fish filets on a clean surface and spread the gochujang onto both sides. Cover in plastic wrap and refrigerate overnight. Wipe off the gochujang and slice the fish into ¼-inch strips.
Make the shrimp balls: In a large bowl, cover the shiitake mushrooms with 12 cups of boiling water. Allow to steep for 30 minutes. Strain the broth into a large pot and save the mushrooms for another use. Add to the mushroom broth white soy sauce, ginger, Sichuan peppercorns, scallions, garlic and star anise and bring to a boil. Reduce to a simmer and cook for 20 minutes. Strain, reserving the liquid.
Meanwhile, in a food processor, pulse the shrimp, lard, sherry, white soy sauce, garlic, ginger, potato starch, sesame oil, black vinegar and egg whites until the shrimp mixture is well combined and very smooth. Transfer to a large bowl.
Using wet hands, form into 1-ounce balls and place onto a parchment-lined baking sheet. Makes 32 balls.
Heat the broth over medium heat. Cook the shrimp balls in the broth, working in batches if needed, for 4 to 5 minutes or until they begin to float. Remove the pot from heat and allow the shrimp balls to cool in the broth.
Make the garlic chive omelet: In a medium bowl, whisk together the eggs, water and sesame oil. Season with salt.
Using a pastry brush, coat the bottom and sides of a 10-inch nonstick skillet with the canola oil and place over medium-low heat. When the pan is slightly hot, add the egg mixture, then cover and cook for 6 to 8 minutes or until the bottom has set but the top is still slightly loose. Top the eggs with the chives, then cover and continue to cook until cooked through and fluffy, 4 to 6 more minutes. Slide the omelet onto a clean work surface; let cool. Slice the omelet into ½-inch-by-1-inch pieces.
Make the hot pot: Place the kombu in a large pot with 12 cups water over medium heat and bring to a simmer. Remove from the heat and steep for 20 minutes. Remove and discard the kombu. Add the bonito flakes and simmer over medium heat for 30 minutes. Using a large fine-mesh sieve or slotted spoon, remove and discard the bonito flakes. Add the reserved fish bones, shrimp shells, scallop side muscles, ginger, scallion and garlic, and simmer for 1 hour. Strain and discard the solids; season with the white soy sauce. Combine the broth with the shrimp balls and their cooking liquid.
To serve, lay out the scallops, sea bass, mackerel, shrimp balls and omelet. Bring the broth to a simmer and add the watercress and noodles. Dip items into the hot broth and serve with soy sauce, black vinegar, chile oil and sesame oil.