In a food processor or a blender, process the olives, shallots, lemon juice, mustard, and zest to a coarse puree. With the machine on, add the olive oil in a slow, steady stream through the feed tube or blender top. Season to taste with salt and pepper. Let the flavors blend together for at least ½ hour before serving.
The sauce will keep for about 5 days, refrigerated.
© 2008 Jayne Cohen. All rights reserved.