2 teaspoons tarragon vinegar, or white-wine vinegar
1 teaspoon anchovy paste, or minced anchovy fillet
8 cups bite-size pieces green leaf lettuce
12 ounces peeled and deveined cooked shrimp, (21-25 per pound; see Ingredient note)
1/2 cucumber, sliced
1 cup cherry or grape tomatoes
1 cup canned chickpeas, rinsed
1 cup rinsed and chopped canned artichoke hearts
1/2 cup chopped celery
Puree avocado, buttermilk, herbs, vinegar and anchovy in a blender until smooth.
Divide lettuce among 4 plates. Top with shrimp, cucumber, tomatoes, chickpeas, artichoke hearts and celery. Drizzle the dressing over the salads.