This is an easy, classical sauce from the south of France that you can whip up in a blender or food processor. It's so little work and time that you can easily squeeze this in on a weeknight. Serve it with cold meats, grilled meats, or fish. Use it sparingly, as a drizzle or dip: it's powerful in taste (and calories.) You may wish to cut the recipe in half.
Olive oil is the dominant ingredient -- and taste -- in this sauce, so you'll want to use one that is table and condiment (as opposed to general cooking) quality. If you use a heavy cooking quality olive oil, the taste and texture may be unpleasantly heavy for many people. Use up within a day or two owing to the raw egg in it. To cut this recipe in half, use 3 oz (90 ml) of olive oil. You can use pasteurized eggs if you are concerned about the raw egg yolk. If you're using anchovies that were preserved in salt, rinse them first before using. Classically, the garlic and anchovy would have been puréed in a mortar, then the mixture transferred to a larger bowl with the recipe proceeding with the aid of a whisk. If the anchovy, garlic and water doesn't form a purée for you in the first step, don't worry, as any small morsels of garlic still intact will get blended in when the oil is added.