Pour half a cupful of sweet oil into an earthen bowl with the juice of half a lemon, half a tablespoonful of salt, and a scant teaspoonful of pepper. Beat well with a spoon or whisk, adding one teaspoonful of parsley, half the quantity of chervil, the same of tarragon and chives all chopped very fine together, and a teaspoonful of mustard. Mix the whole well before serving.