Put the fish in a shallow heatproof dish, such as a large baking pan. Season lightly with salt and pepper, inside and out. Disperse the scallions and ginger on top, underneath, and inside the fish. Combine the soy sauce, peanut oil, sesame oil, and sugar in a bowl. Pour the mixture over the fish.
Set a roasting rack in a large roasting pan. Fill the pan with water that comes up below the rack. Set the pan over 2 burners and bring the water to a boil. Set the baking dish with the fish on the rack, reduce the heat to a simmer, and cover the roasting pan tightly with foil. Steam the fish until a small knife or skewer can be easily inserted into the thickest part and the fillet comes off the bone fairly easily, 6 to 7 minutes.
This recipe was provided by professional chefs and has been scaled down from a bulk recipe provided by a restaurant. The Food Network Kitchens chefs have not tested this recipe, in the proportions indicated, and therefore, we cannot make any representation as to the results.