Wash the potatoes and cut them into one-quarter-inch-thick slices. Cook the sliced potatoes in boiling salted water until tender but not falling apart, about 10 minutes.

While the potatoes are cooking, make the vinaigrette: In a large bowl, combine all the ingredients.

Drain the potatoes in a colander. While they are still warm, add them to the vinaigrette, tossing gently to coat. Set aside to cool.

Preheat the oven to 350 degrees Fahrenheit.

Arrange the prosciutto slices in a single layer on a baking sheet. Roast until

brown and crisp, about 10 minutes. Set aside to cool.

Trim the string beans and cut them in half. Blanch the beans in boiling salted water for 3 minutes Drain in a colander and cool under cold running water. Drain thoroughly.

Crumble the prosciutto into the potato salad. Add the string beans, olives, and parsley and toss to combine. Leftover salad will keep, covered, in the refrigerator for 1 day.