Cook halibut as desired and top with Creamy Mushroom and Herb Sauce.
In saucepan, heat butter and saute onions and mushrooms. Add wine or stock, tarragon, basil, salt and pepper. Simmer for 3 minutes. Add milk and bring to a simmer. Combine cornstarch with cool water to make a paste. Stir into sauce and simmer for another 3 minutes.