yolk of 1 egg raw (some use 2 or 3) 1/2 - 1 teaspn. salt
1 cup to 1 pt. of oil 1 - 1 1/2 tablespn. lemon juice to each cup of oil
Use only 1 cup of oil unless a very thick dressing is required.
Have all utensils and ingredients cold. In very hot weather only, set dish in which dressing is made on chopped ice or in ice water. Use a soup plate with a silver or wooden fork, or a bowl with revolving egg beater. Beat yolk of egg and salt, add 1/2 - 1 teaspn. lemon juice, mix well, then add oil, drop by drop at first, stirring constantly (one way, some say). After a little, oil may be added faster. When mixture becomes thick, stir in a little lemon juice. Do not allow it to get too thick before adding lemon juice. When done the dressing should drop, not pour, from a spoon.
If mixture shows signs of curdling, set dish on ice, continuing to stir, and if it does not become smooth then, add a teaspoon of cream or a little white of egg or a few drops of lemon juice, beating well. Or, take another yolk, begin again more carefully, and when well started add the curdled portion slowly.
If a hard boiled yolk is crushed and worked smooth with a spatula and mixed thoroughly with the raw yolk, the dressing is not so apt to curdle and the oil may be added a little more rapidly.
The tendency to curdling is very much lessened by adding the lemon juice to the yolk before any oil is added.
1/4 - 1/2 cup of heavy cream, chop into it the beaten yolk of an egg, add salt and lemon juice to taste. Chopped parsley may be sprinkled through the dressing, or a little green or red vegetable coloring may be used in it.