arugula, potato and green bean salad

INGREDIENTS

• 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