Place 2 - 3 pounds of Halibut fillets in a lightly oiled dish. Top with thinly sliced onion. Combine ¾ cup mayonnaise and ¾ cup sour cream with entire contents of Midnight sun Halibut Mix . Spread on top of Halibut. Bake in preheated 350 degree oven for 30 - 50 minutes depending on thickness until Halibut flakes. Do not overcook. Garnish lightly with parsley and/or lemon. Serve promptly.