This sauce is indispensable to any one who wishes to use up slices of cold mutton. Trim your slices, take away skin and fat and pour on them the following cold sauce. Hard-boil three eggs, let them get cold. Crumble the yolks in a cup, adding slowly a tablespoonful of oil, salt, pepper, a little mustard, a teaspoonful of vinegar; then chop the whites of egg, with a scrap of onion, and if you have them, some capers. Mix all together and pour it over the cold meat.