Heat the oil in a large frying pan. Add the chicken and fry for 4-5 mins until golden. Transfer to a plate. Add the button mushrooms and onions to the pan and fry, stirring for 5 mins until browned.
Return the chicken to the pan. Stir in the red wine, stock, tomato purée and garlic. Simmer for 20-25 mins until the chicken and onions are tender. Stir in the blended cornflour. Simmer for 2 mins until thickened. Garnish with sprigs of parsley. Serve with diced fried potatoes and vegetables.