Fill the bottom of a double boiler about halfway with water and bring to a boil over medium heat. Reduce the heat to low and put the egg yolks in the top of the double boiler. Cook for 2 to 3 minutes, whisking constantly, until the yolk thickens and begins to bubble around the edge. (This can also be done with the egg yolk in a bowl suspended over a saucepan; be sure the boiling water in the saucepan does not touch the bottom of the bowl.) Beat in the lemon juice and salt and cook for about 30 seconds more, whisking, until the juice is completely incorporated. While continuing to whisk, remove the pan from the heat. Slowly add the oil in a thin stream, about a teaspoonful at a time, whisking until each teaspoonful is absorbed before adding the next. Continue until about half the oil has been added and the mixture has thickened to the consistency of cream. It is vital to whisk constantly from the time you first put the egg yolk over the boiling water until this stage is reached; now is the time to give your wrist a little rest. Whisk in the remaining oil a tablespoonful at a time, until completely incorporated into the mixture, then whisk in the boiling water. The mayonnaise should be ready to use immediately and can be kept in the refrigerator for about 3 days.

any flavored oil for the olive oil, or by substituting 2 tsp of any flavored vinegar for the lemon juice.

For Herb Mayonnaise, put 3 Tbsp fresh Fines Herbes (see recipe) into a fine sieve and blanch by pouring 1 cup boiling water over. Drain and whisk into the mayonnaise after the boiling water has been added.