Marinate the fish: Pat the sea bass fillets dry. Mix with salt, cooking wine, shredded ginger, and cornflour. Marinate briefly for about 10 minutes.
Prepare the egg mixture: Gently whisk the eggs, then mix with the water and a pinch of salt. Do not overmix, as this will create bubbles.
Strain and steam the eggs: Strain the egg mixture through a fine-mesh strainer into a heatproof dish. Use a teaspoon to remove any bubbles on the surface to ensure a silky texture. Steam over boiling water on medium-low heat for 10β12 minutes, until the eggs are just set. Keep the lid slightly ajar (prop it open with a chopstick) to prevent large bubbles from forming.
Add the fish: Once the egg has partially set, gently place the fish fillets on top without overcrowding. Cover the lid fully and steam for a further 5 minutes. Turn off the heat and let it rest for 2β3 minutes to finish cooking gently.
Mix the sauce: Combine soy sauce, water, sugar, and sesame oil in a small bowl. Adjust to taste.
Finish and serve: Drizzle the sauce over the steamed egg, garnish with shredded spring onion, then heat the vegetable oil until very hot. Pour the hot oil over the spring onion to release its fragrance before serving.