Prepare the fish: Rinse the fish thoroughly under cold water and pat dry with paper towels. Make a few diagonal scores on both sides of the fish (if using a whole fish) or on the skin side of fillets. Place the fish on a heatproof plate that fits into your steamer.

Arrange aromatics: Place half of the ginger slices and sliced white parts of scallions inside the fish cavity and on top of the fish.

Steam the fish: Bring water to a rolling boil in a wok or large pot with a steamer rack. Carefully place the plate with the fish onto the steamer rack. Cover and steam for 8-12 minutes, or until the fish is opaque and cooked through. Cooking time will vary depending on the thickness of the fish.

Prepare the sauce: While the fish is steaming, combine light soy sauce, dark soy sauce, sesame oil, sugar, and water/broth in a small bowl. Stir until sugar dissolves.

Finish the dish: Once the fish is cooked, carefully remove the plate from the steamer. Discard the cooked ginger and scallions from the fish, and drain any excess liquid from the plate.

Garnish and serve: Top the steamed fish with the julienned fresh ginger and green parts of scallions. Heat the vegetable oil in a small saucepan until it's very hot (just smoking). Carefully pour the hot oil over the ginger and scallions on the fish – it will sizzle.

Dress and enjoy: Pour the prepared sauce evenly over the fish. Garnish with fresh cilantro if desired. Serve immediately with steamed white rice.