Aioli, the famous garlic mayonnaise of Provence

4-6 large garlic cloves, peeled
2 egg yolks, lightly beaten--at room temperature
about 2 cups olive oil--at room temperature
lukewarm water
juice of 1 lemon

Pound the garlic cloves to a paste. Add the egg yolks. Mix in a bowl with a wooden spoon (or use a marble mortar and wooden pestle), always turning in one direction, until the garlic and eggs have assimilated and are just beginning to get pale. While doing this, add about 4 Tbsp. of oil, very very slowly, drop by drop. The mixture should be thick. Add 1 Tbsp of water and 1 tsp of lemon juice and continue stirring, adding the oil in a very thin stream. When the mixture gets too thick again, add 1 more tsp. each water and lemon juice. Repeat until all oil is used. If the mayonnaise separates, Put it into a clean bowl. Add a garlic clove, 1 tsp of lukewarm water, and 1 egg yolk. Crush and mix together. Add the separated mayonnaise by teaspoons to the bowl, stirring constantly in one direction.

From: Nika Hazelton's Way with Vegetables