Creamy Potato Salad

Bring a large pot three-fourths full of salted water to a boil over high heat. Add the potatoes and boil until tender when pierced with a fork, 15 to 20 minutes. Drain and let cool completely in the refrigerator for at least 1 hour. Cut the potatoes into ¾-inch dice. In a large bowl, stir together the yogurt, mayonnaise, sour cream, mustard, lemon juice, green onions, celery, and the chopped parsley, mint and basil. Add the potatoes. Season with salt and pepper and toss gently to mix. To serve, transfer the salad to a large serving bowl and garnish with parsley, mint and basil sprigs.