Season the pieces of chicken and sauté them in butter and oil. Arrange in a deep dish, cover and keep warm.
In the same pan quickly cook 125 g (4½ oz) sliced mushrooms then add 3 finely chopped shallots; moisten with 1 dl (3½ fl oz or ½ U.S. cup) white wine and ¼ dl (1 fl oz or ⅛ U.S. cup) brandy and reduce by half. Add 1 dl (3½ fl oz or ½ U.S. cup) tomato-flavoured Sauce Demi-glace and a pinch of chopped tarragon and chervil. Pour this sauce over the chicken and sprinkle with a little coarsely chopped parsley.