Combine the green onions, parsley, lemon zest, lemon juice, garlic, egg, salt, and pepper in a food processor or blender and process until smooth. With the motor running, pour the oil through the feed tube in a slow steady stream. The mixture will thicken.
Transfer to an airtight container and refrigerate for 30 minutes before using. Best used within 24 hours.
Yield: 1 1/2 cups