Required: One hard-boiled yolk of egg. One tablespoonful of milk or cream. One teaspoonful of mustard. One teaspoonful of castor sugar. Half a teaspoonful of salt. Four tablespoonfuls of the best olive oil. Three tablespoonfuls of vinegar.
Mix the mustard smoothly with the milk, then add the sugar and salt. Rub the yolk of an egg through a sieve, and mix it with the mustard, etc.; then add the oil slowly; lastly, add the vinegar very gradually, stirring all the time, otherwise it will curdle. Pour the " dressing" into a bottle, and shake it well.
N.B.-This sauce is preferred by many to mayonnaise, because it has a less oily flavour. If tightly corked it will keep for weeks.