Soak mushrooms in boiling water 20 minutes; remove stems. Put softened mushrooms, oyster sauce, and sherry into a bowl; stir.
Let mixture sit for 10 to 20 minutes.
Preheat oven to 400 degrees F (200 degrees C). Line a large baking dish with foil, then lightly grease it with olive oil or nonstick cooking spray.
Place salmon fillets in prepared baking dish and pour mushroom mixture over the salmon.
Bake in the preheated oven until fish flakes easily, about 10 to 12 minutes. If desired, at the end of the cooking time, broil the salmon to sear the coating, about 1 to 2 minutes.
