About 1.25 hours before serving: Discard bones and skin from chicken; cut meat into bite-sized pieces. Cut potatoes into 1 cm chunks; set chicken and potatoes aside. Preheat oven to 200ºC . Slice mushrooms, carrots and celery; chop onion. In a 30 cm skillet over high heat, in hot salad oil, cook mushrooms, carrots, celery and onion for 5 minutes, stirring frequently, until vegetables soften slightly; stir in flour, salt, chicken bouillon, dried thyme and pepper until vegetables are well coated. Add chicken, potatoes and 3.3333333333333 cups milk to mixture in skillet; over high heat, heat to boiling. Boil one minute. Spoon chicken mixture into a deep 3 litre casserole; bake, uncovered, for 10 minutes. Meanwhile, prepare corn-muffin mix according to label, using egg and remaining two third cups milk. After chicken mixture has baked 10 minutes, remove casserole from oven and spoon cornmeal mixture over the top of chicken mixture. Bake 15 minutes longer or until cornmeal crust is golden and chicken mixture is hot and bubbly. ~-