Makes 8 small salads or 4 larger ones
1 ounce walnuts (about 1/3 cup)
1 1/2 pounds fingerling potatoes, cut crosswise into 1/2-inch-thick rounds
6 ounces haricots, verts, or other green beans, trimmed and cut into 2-inch segments
2 tablespoons white wine or other mild vinegar
2 tablespoons plain yogurt
1 teaspoon Dijon mustard
1 teaspoon coarse salt
Freshly ground pepper
2 tablespoons walnut oil
3 ounces baby arugula
Preheat oven to 375°. Place walnuts on a rimmed baking sheet and toast in oven until fragrant, about 8 minutes. Let cool slightly, then coarsely chop and set aside.
Bring a medium saucepan of water to a boil. Add potatoes, and cook until tender, about 10 minutes. Using a slotted spoon, transfer potatoes to a colander to drain and cool. Set aside.
Prepare an ice-water bath; set aside. Return pan of water to a boil. Add green beans, and cook until tender and bright green, about 3 to 4 minutes. Using a slotted spoon, transfer to ice-water bath to stop the cooking. Drain.
Whisk together vinegar, yogurt, mustard and 1/2 teaspoon salt in a small bowl; season with pepper. Add oil in a slow, steady stream, whisking until emulsified. Set dressing aside.
Arrange arugula, potatoes, and green beans on a platter. Season with remaining 1/2 teaspoon salt and 1/4 teaspoon pepper. Drizzle with dressing and sprinkle with toasted walnuts; toss to coat.