Chop fine the parsley, onions and anchovies. Lay them in a bowl and mix with salt and mustard to taste, the salad oil and vinegar. Stir all well together and then add, one at a time, some very thin strips of cold roasted or boiled meat, not more than three or four inches long. Shake the slices well in the dressing. Cover the bowl closely and allow to stand for at least three hours. Serve garnished with parsley.