Place bass in a shallow glass or enamel container. Combine remaining ingredients, except parsley. Marinate 2 hours, turning steak over after 1 hour. Bring water under a steamer rack to a rollingboil, add ginger, garlic and scallions.
2
Baste fish with soy-sherry mixture as you place it on the steamer rack. Cover and steam approximately 10 minutes for each inch thickness. Garnish with freshly chopped parsley and slivered lengthwise scallions.