In a wide, shallow bowl, stir together the chopped cilantro, minced scallions, ginger, 2 tablespoons of the soy sauce and 1 tablespoon of the grapeseed oil. Add the fish and coat on all sides. Let stand at room temperature for 10 minutes.

Place a folding steamer basket in a large Dutch oven. Add enough water to fill the bottom of pot without submerging the basket. Remove the basket. Cover the pot and bring to a simmer over medium-high.

Line the basket with 4 of the cabbage leaves. Place the fish fillets on the leaves, then cover with the remaining 2 leaves. Turn off the heat under the pot, then set the basket in it. Cover and return to a simmer over medium. Steam until the fish flakes easily, 8 to 12 minutes.

Meanwhile, in a small bowl, whisk the remaining 4 tablespoons soy sauce, the rice vinegar, sugar and white pepper. Transfer 3 tablespoons of the mixture to a medium bowl, add the sliced cabbage and toss.

Arrange in an even layer on a serving platter. Reserve the remaining soy sauce mixture for serving.

When the fish is ready, discard the cabbage leaves covering it. Using a spatula, transfer the fillets to the platter over the cabbage. Sprinkle with the sliced scallions and the serrano.

In a small skillet over medium-high, heat the remaining 2 tablespoons grapeseed oil until beginning to smoke. Immediately pour the oil over the fillets.

Drizzle with the sesame oil and sprinkle with the cilantro leaves. Serve with the reserved soy sauce mixture on the side.