Heat oven to 350 degrees. Put 2 tablespoons butter and 2 tablespoons oil in baking dish and put in oven. When butter is melted, add 6 boneless, skinless chicken breast halves, turning to coat with butter. Bake for 35 minutes (maximum) uncovered. Pour off fat. Combine the following in a large saucepan:

1 can condensed cream of chicken soup
1/2 c. light cream or half & half
1/2 c. dry sherry
1 tsp. tarragon leaves
1 tsp. Worcestershire sauce
1/4 tsp. garlic powder
6 oz. sliced mushrooms, drained

Cover tightly and cook 10-15 minutes longer.