This sauce evokes Provence at its productive best, in spring and summer, when farms and family gardens are at their peak production, yielding vegetables with an incomparable depth of flavor.
ASTUCE - When making aioli - or any mayonnaise-like sauce - think slow, slow, slow. There is a simple remedy for separated aioli. Put an egg yolk in another bowl and slowly whisk the separated aioli into it.
Make a paste of the garlic and salt in a mortar and pestle, by working the pestle around slowly, always in the same direction, in the mortar. If you don't have a mortar and pestle, either finely mince the garlic with the salt, transfer it to a medium-sized bowl and press on it with a wooden spoon until it makes a rough paste, or simply mince the garlic and salt together in a food processor.
If you used a food processor to mince the garlic and salt together, transfer the mixture to a medium-sized bowl. Whisk in the mustard and egg yolks until they are blended with the garlic and salt then, using either the mortar or a whisk, add 1/4 cup (60ml) of the neutral oil very slowly in a fine, fine stream, until the mixture becomes thick. Don't add the oil too quickly or the mixture will not emulsify.
Add 1 teaspoon of the lemon juice to the oil and garlic mixture, then add the remaining oil very, very slowly, whisking or turning the pestle constantly. The aioli will gradually thicken to the consistency of a light mayonnaise. Adjust the seasoning, and add more lemon juice if it needs more tang. If it becomes very, very thick you might add 1 tablespoon warm water, to loosen it.
Taste for seasoning, and adjust with salt if necessary. Aioli will keep for several days in the refrigerator, in an airtight container, but it is best served within 24 hours of being made.