Chicken salad with grapes and walnuts

Active time: 35 min Start to finish: 35 min

4 cups cubed (1/2 inch) cooked chicken (about 1 3/4 lb)
1 cup walnuts, toasted and chopped
1 celery rib, cut into 1/4-inch-thick slices (1 cup)
2 tablespoons finely chopped shallot
2 cups halved seedless red grapes
3/4 cup mayonnaise
3 tablespoons tarragon vinegar
2 tablespoons finely chopped fresh tarragon
1/2 teaspoon salt
1/2 teaspoon black pepper
Toss together all ingredients in a large bowl until combined well. 
Makes 4 to 6 servings.