Reduce, by two-thirds, four-fifths of a pint of white wine containing four chopped shallots, fragments of thyme and bay, and four ounces of mushroom parings. Add four-fifths pint of veal gravy, reduce the whole to half, rub it through sieve, and finish it away from the fire with eight ounces of Maitre d'Hôtel butter and a dessertspoonful of chopped tarragon.