In a casserole, heat butter and oil and brown chicken; season with salt and pepper if desired. Warm brandy in saucepan, ignite, and pour over chicken. Allow flame to burn itself out. Add apples and onion. Combine cider, sour cream, flour, and herbs; stir until smooth and pour over contents of casserole. Bake, covered, at 350 degrees for 1 hour, or until chicken is tender. If you want, 2 cups of cider or apple juice may be used; just omit the sour cream and use 2 Tbs of flour. You can also try it without the tarragon, using 1/4 tsp each of nutmeg, cinnamon, and ground cloves. Serve with: French bread watercress or spinach salad