Prepare the fish: Ensure the whole fish is scaled, gutted, and cleaned. Pat it dry thoroughly with paper towels. Make 2-3 diagonal scores on both sides of the fish. You may also rub a pinch of salt and pepper on the fish, if desired. Place some ginger slices and the white parts of julienned scallions inside the fish cavity and on top of the fish. Steam the fish: Place the fish on a heatproof plate. Bring about 2-3 inches of water to a rolling boil in a wok or large pot with a steamer rack. Carefully place the plate with the fish onto the rack, cover tightly, and steam for 8-12 minutes, depending on the fish's thickness, until it is opaque and flaky at its thickest part. Prepare the sauce: While the fish steams, combine light soy sauce, sugar, and water in a small bowl. Stir until the sugar dissolves. If using, add the sesame oil to this mixture. Garnish and sizzle: Once steamed, carefully remove the fish plate from the steamer. Discard any excess liquid that has accumulated on the plate. Top the fish generously with the remaining julienned ginger, julienned scallions (green parts), and fresh cilantro. Heat the oil: In a small saucepan, heat the neutral oil over high heat until it is smoking hot (you should see wisps of smoke). This typically takes 2-3 minutes. Pour and serve: Carefully pour the smoking hot oil directly over the ginger, scallions, and cilantro on the fish. You should hear a dramatic sizzle. Immediately drizzle the prepared soy sauce mixture evenly over the fish. Serve the Sizzling Ginger Steamed Fish immediately with steamed rice.