For the Green Goddess Dressing
4 anchovy fillets, chopped
2 green onions, green parts only, finely chopped
1-1/2 tablespoons chopped parsley
2 tablespoons chopped tarragon
2 tablespoons tarragon vinegar
2 tablespoons minced chives
1-1/2 cups mayonnaise
For the Shrimp and Potato Salad
1-1/2 pounds fingerling potatoes
1 teaspoon salt
2 teaspoons tarragon vinegar
1/2 cup white wine
2 cups water
1/3 cup loosely packed trimmings from the dressing (equal parts green onions, tarragon and parsley)
1 pound shell-on shrimp
1/2 pound cherry or grape tomatoes, cut in half lengthwise
2 teaspoons snipped chives
For the Dressing
In a food processor or blender, purée the anchovies, green onions, parsley, tarragon, vinegar and chives, or grind with a mortar and pestle to make a fairly smooth paste.
Stir the mixture into the mayonnaise. Refrigerate tightly covered.
For the Shrimp and Potatoes
Bring water to a simmer in a double boiler. Slice the fingerlings in half lengthwise. If they are more than 3 inches long, cut them in half again crosswise.
Steam, covered over medium heat until tender, 12 to 14 minutes. Transfer to a large mixing bowl and season with salt and tarragon vinegar. Toss to coat well and set aside at room temperature to cool.
In a medium saucepan, bring the white wine with 2 cups of water and herb trimmings to a simmer over high heat. Immediately reduce the heat to bring the contents to a gentle simmer, and simmer, covered, for 10 minutes to allow the contents to steep. Add the shrimp, cover tightly and simmer for 3 minutes before removing the pan from the heat. Let stand, covered, until the shrimp are firm but cooked through, about 15 minutes. Drain, peel and refrigerate in a tightly sealed bag or covered container.
Just before serving, add the shrimp to the potatoes. If the shrimp are large, they should be cut into bite-size pieces.
Stir in the Green Goddess dressing. You won't use all of the recipe, so start with one-third cup, then add more dressing a tablespoon at a time until the shrimp and the potatoes are lightly napped, but not gloppy with mayonnaise. It will take about one-half cup total.
Gently fold in the tomatoes, and sprinkle with snipped chives. Serve immediately or refrigerate, tightly covered, and bring to cool room temperature before serving.