Melt 2 tablespoons butter in a pan with the salad oil and fry bacon until crisp. Remove bacon from pan and drain on paper toweling. Brown the chicken pieces in the fat, turning once. Put chicken pieces and bacon in a 2-quart baking dish.
Fry onions and celery in the fat remaining in the pan until soft, then add to the baking dish. Melt remaining tablespoon butter in the pan, add mushrooms and sauté for 2 minutes; remove and drain on paper towels.
Blend garlic and flour in fat remaining in pan, and cook gently until browned. Add wine, broth, and herbs, and season to taste. Simmer gently until mixture thickens slightly. Pour over chicken in the casserole. Cover baking dish and bake for 2 hours in a 350-degree oven. Stir mushrooms into casserole; cool.
To Freeze: Freeze in freezer/oven safe casserole dish.
To Reheat: thaw overnight in refrigerator, or 4 to 5 hours at room temperature. Place covered casserole in 350-degree oven for 1 to 1 1/4 hours, until bubbling and hot.