Cook the chicken and potatoes a day before serving so you can easily mix and be picnic ready!
In a large bowl, add the yogurt, mayo, apple cider vinegar, sugar, garlic salt, pepper, potatoes, tomatoes, celery, onion and mix well. Set aside.
In a medium bowl combine the chicken and pesto and toss until chicken is coated. Add the chicken mixture to the large bowl and toss to combine. Garnish with fresh sliced basil to add both flavor and color.