Ingredients

　　4 cups cubed (1/2 inch) cooked chicken (about 1 3/4 pound)

　　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.