- 3/4 pound green beans, trimmed
- 3 pounds cooked small (2-inch) boiling potatoes, cooled to room temperature and quartered
- 1 cup mayonnaise
- 3 tablespoons tarragon vinegar or white-wine vinegar
- 3 scallions, chopped
- 3 flat anchovy fillets, chopped, or 2 teaspoons anchovy paste
- 1/4 cup chopped fresh flat-leaf parsley
- 2 teaspoons chopped fresh tarragon
- 1 teaspoon salt
- 1/2 teaspoon black pepper
- Cook beans in a 3-quart saucepan of boiling salted water , uncovered, until crisp-tender, 3 to 5 minutes. Drain in a sieve, then plunge sieve into a large bowl of ice and cold water to stop cooking. Drain again. Pat beans dry, then cut into 1/4-inch pieces and put in a large bowl along with potatoes.
- Pulse mayonnaise, vinegar, scallions, anchovies, parsley, tarragon, salt, and pepper in a food processor until dressing is pale green and herbs are finely chopped. Stir into potato mixture.