For a delicious variation, you can add a couple of big spoonfuls of peanut butter to this instead of the walnuts, toss in a chunk of ginger and a splash each of soy sauce and maple syrup, and swap in vegetable oil for olive. It changes the character of the sauce completely, to something more like a green peanut sauce, and it’s lovely that way, too.
- In a food processor or powerful blender, whir together the cilantro, vinegar, garlic, salt, cayenne, and walnuts, stopping the motor occasionally to scrape down the sides of the bowl with a rubber spatula. With the motor running, drizzle ¼ cup oil through the feed tube and process, adding more oil if you need or want to, until emulsified. Taste for seasonings and add more salt, vinegar, or spice as needed.