Preheat oven to 400 degrees Fahrenheit.
Arrange the chicken in a baking dish and pour-in chicken stock.
Bake the chicken for about 40 to 45 minutes.
Turn off the oven and remove the chicken. Let cool.
Drain excess liquid then cut the chicken into cubes.
In a mixing bowl, combine sour cream, mayonnaise, tarragon, salt, and ground black pepper. Mix well.
Add in celery, apple, grapes, walnuts, and chicken then stir to distribute the ingredients.
Refrigerate for at least 1 hour.
Transfer to a salad plate the serve.
Share and enjoy!