Place in a stewpan one ounce of chopped shallots, a sprig of thyme and a bit of bay, one ounce of mushroom parings, and one-quarter pint of white wine. Reduce the wine almost entirely, add one-half pint of veal gravy, and reduce again until the liquid only measures a gill. Strain through muslin, and finish the sauce away from the fire with four ounces of butter "Maitre d'Hôtel," to which add a little chopped tarragon. Serve with grilled fillet of beef.