Mayonnaise is a delicious cold sauce and is used in so many dishes that it is really worthwhile making it yourself. There is no secret to getting mayonnaise to thicken: it works on the simple basis that as the oil is whisked into the egg yolk, a creamy emulsion is formed. If you add the oil too quickly or the eggs are too cold the emulsion breaks down and the oil separates out. It doesn’t spoil the flavour but it looks unappetizing. Start again with a clean bowl and a fresh egg yolk and slowly whisk the separated mixture into the egg yolk and it will thicken perfectly.
Oil olive oil or corn oil is best and egg yolk are the basic ingredients. White wine vinegar, cider vinegar or a herb-flavoured vinegar (especially tarragon) or lemon juice is added to thin the mixture. Salt and freshly milled pepper are the basic seasonings, and a little prepared French or English mustard is added which encourages the mixture to form an emulsion. You can also add herbs, garlic, tomato and other flavours to suit your tastes.
Have the ingredients at room temperature.
Use a heavy small mixing bowl and stand it on a folded damp cloth or sponge so it stays firmly in place. Use a coil-rimmed hand whisk or fork for heating the oil. Your other hand is then free for adding the oil.
Whisk together the egg yolk, seasoning, a little mustard and some of the vinegar or lemon juice before adding any oil.
Measure the oil into a jug, and then you can pour it slowly. Add the oil a few drops at a time initially. Then as soon as the mayonnaise begins to thicken, you can pour the oil in a thin steady stream by holding the jug high above the bowl.
Halfway through whisking, add the rest of the vinegar to thin the mayonnaise.
A little boiling water added at the very end makes mayonnaise lighter in texture.
If making mayonnaise in a blender and you have a choice of speeds, keep the speed set at low as a high speed will result in a thin mayonnaise. With a blender you can make mayonnaise more economically by using 1 whole egg but the best results still come from using 2 egg yolks. Make large quantities when making mayonnaise in an electric blender.