Chicken Salad with Grapes

Name: Chicken Salad with Grapes
Prep time: 15 min
Cook time: 4 min
Total time: 19 min
Cuisine: American
Ingredients: 1/2 cup pecan or walnut halves; 1/2 cup sour cream, whole milk plain yogurt or plain Greek yogurt; 1/3 cup mayonnaise; 1 tablespoon Dijon mustard; 2 teaspoons packed light brown sugar; 1/4 teaspoon kosher salt, plus more as needed; 1/4 teaspoon freshly ground black pepper, plus more as needed; 4 cups cooked chicken (about 20 ounces); 1 medium shallot; 2 ribs medium celery; 1 1/2 cups red seedless grapes (about 6 ounces)