1/2 cup mayonnaise
      1/2 cup sour cream
      1/2 cup tahini
      1/4 cup fresh lemon juice
      6 anchovy fillets (from 1 [2-ounce] can)
      1 cup loosely packed fresh basil leaves
      1 cup loosely packed fresh flat-leaf parsley leaves
      1 cup loosely packed fresh cilantro leaves and tender stems, plus
      more for garnish
      4 scallions, chopped (about 1/2 cup)
      1/4 cup chopped fresh dill, plus more for garnish
      1 1/4 teaspoons kosher salt, plus more to taste
      1/4 teaspoon black pepper, plus more to taste
      2 small (1-pound) iceberg lettuce heads, outer leaves removed,
      each head cut through core
      into 6 wedges
      2 Persian cucumbers, thinly sliced (about 1 1/2 cups)
      6 medium radishes, thinly sliced (about 1 cup)
      Toasted sesame seeds, for garnish
    
Process mayonnaise, sour cream, tahini, lemon juice, and
      anchovies in a food process
      or until anchovies are finely chopped, about 1 minute.
      Add basil, parsley, cilantro, scallions, dill, salt,
      and pepper; process until smooth and light green in color, about 1
      minute. Transfer dressing to
      a bowl. Cover and refrigerate until well chilled, about 20 minutes