[Please only use extra virgin olive oil. Just about any corn oil on your supermaket shelves these days is unfit for consumption.]

Break an egg into a bowl, beat steadily with a rotary motion until it begins to thicken, then drip in slowly olive or corn oil, stirring in one direction all the while.  When it thickens add the oil more rapidly, also strained lemon juice to taste.  Never add more oil until the preceding quantify has become thoroughly amalgamated with  the egg, the proportion being about half a pint of oil to an egg.  Should the mayonnaise curdle while you are making it, stop at once, start another egg in a clean bowl, and when it thickens add the curdled mixture by degrees and the whole will result in a good thick mayonnaise.  The curdling is usually due to pouring in too much oil at one time.  If this is avoided and the egg is absolutely fresh and all utensils used dry and cool, no difficulty will be experienced.  The mayonnaise may be colored green or pink as desired by mincing parsley finely and rubbing to a paste with a spoon and adding to the dressing after it is made, or by stirring in a little strained strawberry, raspberry, or beet juice.

[Also see Eggless Mayonnaise]