Persillade Sauce

Place in a small bowl one tablespoonful of mustard and four pounded hard boiled egg-yolks, dilute this gradually with two gills of oil and four tablespoonfuls of vinegar, or the juice of four lemons; add to it salt, pepper and mignonette, some parsley leaves, chervil and tarragon, all finely chopped, and serve the sauce separately. Chopped hard boiled egg-whites are frequently added to this sauce.