How to Make It
In a small skillet, heat 1 tablespoon of the grapeseed oil. Add the shallot and cook over moderately low heat, stirring occasionally, until lightly browned, about 8 minutes. Add the sugar, ginger and garlic and cook, stirring, until fragrant and the sugar is melted, about 2 minutes. Add the soy sauce, vinegar, fish sauce and shio kombu and bring to a boil over moderately high heat, then simmer over moderately low heat until slightly reduced, about 3 minutes. Remove from the heat and stir in the cilantro and scallion.
Set a bamboo steamer in a wok or a large, deep skillet. Add 1 inch of water to the wok or skillet and bring to a boil. Line the inside of the steamer with the cabbage leaves. Combine the sesame oil and the remaining 1 tablespoon of grapeseed oil and brush all over the fish. Season the fish lightly with salt and set it on the cabbage leaves. Cover and steam over moderate heat for about 7 minutes, until just cooked through. Transfer the fish to plates and serve with the ginger-garlic sauce.