This delicately flavoured, uniquely light and smooth mixture of oil, egg yolks and lemon juice is perhaps the most popular of the cold sauces.
Deservedly or not, Cardinal Richelieu is credited with the invention of this sauce in the 17th century, and it is interesting that it is still made in exactly the same way today, except that one may, using great care, combine the emulsion with an electric beater or food processor instead of a wire whisk. Certainly, one should first master the skill of making this sauce in the old way (with a wire whisk) before making it with modern electric beaters.
Making mayonnaise presents only one problem: it may curdle or separate. For consistent success, have the egg yolks and oil at room temperature, and beat the oil into the egg yolks very gradually, drop by drop at first then finally in a thin stream, until the emulsion of the egg and oil forms a smooth sauce. If anything goes wrong and the mayonnaise separates, you can restore the emulsion as follows: wash the beater; in another bowl beat another egg yolk with ½ teaspoon salt and ½ teaspoon vinegar; then gradually beat in the curdled mayonnaise 1 teaspoon at a time at first, then more quickly until emulsified.
Mayonnaise should be stored in a cool place, not in the refrigerator. It will keep for several weeks – the oil is a preservative. Mayonnaise has dozens of uses, can be varied endlessly and will transform such simple ingredients as hard-boiled eggs, fresh cooked or tinned fish, poached chicken or diced cooked vegetables into an elegant dish. There are many lovely variations; some of the classics are sauce rémoulade, sauce tartare, sauce niçoise, aïoli sauce, sauce russe and sauce à la Ritz.