Notes: Chef Peter DeMarais uses reduced-fat sour cream to make a tangy dressing; regular mayonnaise produces a mellower blend. Chervil gives the dressing a subtle licorice flavor; if it's unavailable, delete it and increase tarragon leaves to 1 cup.
In a blender or food processor, combine mayonnaise, spinach leaves, parsley, tarragon leaves, chervil, lemon juice, shallot, and anchovies. Whirl until very smooth. Serve, or chill airtight up to 1 week.
Nutritional analysis per tablespoon.