Heat half the oil in a large frying pan over medium heat. Cook the chicken, in 2 batches, for 5 minutes or until golden then transfer to a plate.
Heat remaining oil in the pan. Add the mushrooms. Cook for 5 minutes or until golden. Add celery, shallot and garlic. Cook, stirring occasionally, for 3-5 minutes or until soft.
Stir in the tomato paste and cook for 2 minutes. Add the wine and cook, scraping base of pan with a wooden spoon, for 2 minutes or until reduced by half. Add the tomato, stock and thyme. Bring to the boil. Return the chicken to the pan and simmer for 15 minutes or until sauce thickens slightly. Season. Stir in parsley. Serve with couscous and beans, sprinkled with extra thyme.