Season both sides of the salmon. Lay out one leaf of napa on a flat surface. Place 2 mushrooms top side down and cover with salmon, also top side down. Wrap cabbage around salmon. Repeat. This can be done up to 2 hours before cooking. Place in steamer for 8 to 10 minutes. Salmon should be served medium rare. On a large plate, sauce completely and place salmon in the middle. Garnish with orange zest.
In a saucepan coated with oil, saute ginger for 2 minutes then add peppers and scallions. Season then add stock and juices. Reduce by 20 percent. Whisk in butter and check for seasoning. Serve immediately.