Make the Dressing: In a large bowl, stir together the mayonnaise, Greek yogurt (or sour cream), Dijon mustard, lemon juice, salt, and pepper until smooth and creamy.
⅔ cup mayonnaise, 2 tablespoons plain Greek yogurt or sour cream, 1 teaspoon Dijon mustard, ½ teaspoon lemon juice, Salt and black pepper
Mix in the Good Stuff: Add the cooked chicken, celery, grapes, pecans, red onion, and parsley. Gently stir everything until the dressing coats all the ingredients evenly.
3 ½ cups cooked chicken, 2 stalks celery, ⅔ cup red grapes, ½ cup chopped pecans, ½ medium red onion, 2 tablespoons chopped fresh parsley
Chill It Down: Cover the bowl and refrigerate for at least 1 hour before serving. This gives the flavors time to mingle and makes the salad extra tasty.