If whipping up homemade mayonnaise using raw egg yolks isn't for you, here's an alternative, food-safe method.
Traditionally, mayonnaise is made with raw egg yolks—an ingredient many cooks prefer to avoid. Alternative approaches suggest making mayonnaise with hard-cooked eggs and even an eggless mayo with milk. But in his book The Curious Cook, Harold McGee has a novel method in which he heats the yolks to a food-safe 160 degrees, keeping them in liquid form. First the yolks are thinned out a bit with water and lemon juice (which helps stabilize them, as acids prevent curdling). Then they are microwaved briefly until slightly thickened, retaining nearly all their emulsifying power. We tested the technique and it worked well, giving us a billowy, creamy mayo.
HERE'S THE METHOD: Place one egg yolk in a bowl and whisk in 1 tablespoon of water and 1 tablespoon of lemon juice. Cover and microwave for 15 to 20 seconds, or until the egg starts to bubble. Uncover, whisk until smooth, and microwave for 5 seconds, or until the mixture comes to a boil again. Whisk again, cover, and let sit until cool. Add a pinch of salt and then whisk in 1 cup of oil in a thin stream.
NOTE: Use only 1/3 cup or less of extra-virgin olive oil, since it contains trace impurities that can cause the emulsion, which is not quite as stable as a traditional mayo, to break within a few hours. Regular olive oil and other vegetable oils do not present this problem.