This recipe was provided by Jeanne Hicks. She shared several recipes with us at our Evanston store. She also provided a recipe for Cured Flank Steak, included on the site, that is a perfect pair for this sauce.
Combine all ingredients, except olive oil and green onions, in food processor or blender, on high speed. Drizzle olive oil in to form an emulsion. Add the green onions and process until relatively smooth and green.