Autumn Potato Gratin
["3 medium red potatoes, peeled and sliced thin", "2 sweet potatoes (1 lb.), peeled and sliced thin", "1 medium onion, sliced thin", "1 tsp. chervil", "1/2 tsp. summer savory", "salt to taste", "freshly ground pepper to taste", "1/2 c. butter", "2 Tbsp. olive oil", "parsley sprigs for garnish"]
["Arrange half of potato slices in deep 10-inch pie plate.", "Put onion slices on top.", "Sprinkle with chervil, summer savory, pepper, salt, half of the butter and oil.", "Arrange remaining sweet potato slices in overlapping pattern around edge of pan.", "Arrange remaining white potato slices in overlapping pattern in center. Drizzle remaining oil over top.", "Cover with foil and bake at 350\u00b0 for 30 to 35 minutes.", "Uncover and bake 30 minutes more or until golden and tender, basting occasionally with butter.", "Serves 6."]
["red potatoes", "sweet potatoes", "onion", "chervil", "summer savory", "salt", "freshly ground pepper", "butter", "olive oil", "parsley sprigs"]