1. Heat oil in frying pan, add chicken and lightly brown. Set aside on absorbent paper. 2. Add celery, carrot and onion to pan. Stir over heat for 1 minute. 3. Add undrained tomatoes and chicken stock cube, bring to boil. 4. Combine cornflour and 1/5 cup of water and gradually stir into pan until mixture thickens. 5. Add chicken and mushrooms, cover and simmer for 15 minutes until chicken is cooked and tender. 6. Sprinkle with parsley and serve with steamed vegetables.