Step 1Place the garlic in a mortar with a pinch of salt and pound it to a paste. Add the anchovies and repeat. Add the onion, parsley, herbs, vinegar, capers and 1 tablespoon of oil and pound and grind until the paste is smooth. Stirring and grinding with the pestle, add the olive oil in 2 or 3 pours, making sure the sauce is well blended before adding more. Taste for salt and serve.
Food processor or blender: With the machine running, drop the garlic into the feed tube and run until it is finely chopped. Add the anchovies, onion, parsley, herbs, vinegar, capers and half the oil and pulse until pureed. With the machine running, add the remainder of the oil in a steady stream through the feed tube. Scrape down the sides of the work bowl as needed. Taste for salt and serve.