Trim the chicken pieces neatly. Heat the butter in a frying pan, add the chicken and fry gently to brown. Lift the chicken from the pan and arrange in a casserole with the slices of lemon.
Peel and finely chop the onion. Heat the oil in a saucepan, add the onion and cook gently for a few moments until the onion is tender. Measure the remaining ingredients for the sauce into a basin. Ble