The solution: The key technique in making a successful mayonnaise is whisking the oil into the egg mixture. If you add too much too quickly, it won’t be incorporated into the emulsion of eggs and oil that you are trying to create by whisking or mixing. If the oil gets ahead of the eggs’ ability to absorb it, you’ll end up with a pool of oil and a curdly mass of eggs. (See "Drizzling the Oil" for a technique that all but guarantees a slow, steady drizzle of oil).
Another important consideration in terms of both flavor and texture is the kind of oil used. Olive oil produced disappointing results; extra-virgin contributed a harsh flavor to the mayonnaise, while pure olive oil made it somewhat dense and heavy. We ended up liking 100 percent corn oil best. It makes a rich-tasting mayonnaise with plenty of body. Canola oil was good, too, making for a lighter, more lemony mayonnaise.
Also crucial to flavor is the use of freshly squeezed lemon juice; mayonnaise made from reconstituted lemon juice didn’t have the bright flavor of the real thing. (Fresh lime juice works pretty well as a substitute for fresh lemon juice.)
Also crucial to texture is the ratio of oil to liquid. Contrary to what would seem like common sense, more oil makes a stiffer mayonnaise. (If a mayonnaise has become too stiff you can simple whisk in a bit of water to soften it.) We had seen recipes calling for as little as one-half cup of oil per egg yolk and as much as one cup. Three-quarters cup was just right, producing a mayonnaise with a smooth but not stiff consistency and allowing for a distinct yet not overwhelming flavor of egg and lemon.

MASTER RECIPE FOR HOMEMADE MAYONNAISE

Makes 3/4 cup

Each time you add oil, make sure to whisk until it’s thoroughly incorporated, but it is fine to stop for a rest or to measure the next addition of oil. Mayonnaise should have a smooth, uniform consistency. If it appears grainy or beaded after the last oil addition, as if it has broken, continue to whisk and it should emulsify. To keep the bowl stable while whisking, set it on a wet dishcloth.

1 large egg yolk
1/2 teaspoon salt
1/4 teaspoon Dijon-style mustard
1 1/2 teaspoons juice from 1 small lemon
1 teaspoon white wine vinegar
3/4 cup corn oil

Whisk egg yolk vigorously in medium bowl for 15 seconds. Add all remaining ingredients except oil and whisk until yolk thickens and color brightens, about 30 seconds. Adding 1/4 cup oil in slow, steady stream, continue to whisk vigorously until oil is incorporated completely and mixture thickens, about 1 minute. Add another 1/4 cup oil in same manner, whisking until incorporated completely, about 30 seconds more. Add last 1/4 cup oil all at once and whisk until incorporated completely, about 30 seconds more. Serve. (Can be refrigerated in airtight container up to 7 to 10 days.)

LEMON MAYONNAISE

Follow Master Recipe for Homemade Mayonnaise, adding 1 1/2 teaspoons grated lemon zest along with the lemon juice.

Tartar Sauce

Follow Master Recipe for Homemade Mayonnaise, mixing 1 1/2 tablespoons minced cornichons (about 3 large), 1 teaspoon cornichon juice, and 1 tablespoon each minced scallion, minced red onion, and drained minced capers into completed mayonnaise.

TARRAGON MAYONNAISE

Follow Master Recipe for Homemade Mayonnaise, mixing 1 tablespoon minced fresh tarragon leaves into completed mayonnaise.

ROASTED GARLIC MAYONNAISE

Follow Master Recipe for Homemade Mayonnaise, adding puree from 1 medium head (about 3 tablespoons) roasted garlic (see “Roasting Garlic,” September/October 1993) to initial ingredients and substituting 1/4 cup pure olive oil for 1/4 cup corn oil.

FOOD PROCESSOR MAYONNAISE

Makes 1 1/2 cups

Follow Master Recipe for Homemade Mayonnaise, adding 1 whole large egg and doubling quantities of other ingredients. Pulse all ingredients except oil in workbowl of food processor fitted with metal blade three or four times to combine. With machine running, add oil in thin steady stream through open feed tube until incorporated completely.