Soak mushrooms in hot water 20 minutes or until soft; drain and cut into thin strips.
Cut 3 (3/4-inch) deep lengthwise slits in each fillet. Combine cornstarch, salt, and pepper; sprinkle over fish. Let stand 10 minutes. Stuff mushroom strips and green onions into slits.
Place fish in a 9-inch pie plate. Combine sake and the remaining ingredients; pour over fish. Place a bamboo steamer basket in a large wok, and add water to wok to a depth of 1 1/2 inches below basket. Bring the water to a boil. Place pie plate in bottom of steamer basket; cover and cook 8 minutes or until fish flakes easily when tested with a fork.
Wine note: In this dish, the sweet earthiness of the mushrooms and black bean sauce as well as the flavor of the salmon form a perfect counterpoint to the earthy flavors and silky texture of a good pinot noir. Try Sebastiani pinot noir 2002 (Russian River Valley, California), $23, with its forestlike aromas of earth, dried leaves, and underbrush, and its seductive flavors of dried cherries, mocha, and vanilla. -Karen MacNeil