In a large bowl, add the chicken, grapes, walnuts, celery, and scallion. Set aside.
In a small bowl, whisk together all of the dressing ingredients. Pour over the chicken salad ingredients and stir to combine. Make sure to carefully toss so the chicken doesn't break up too much.
I suggest letting this sit in the fridge for at least one hour. Serve and enjoy.
*If you like a "smoother" consistency to your chicken salad, instead of dicing the chicken into chunks, shred it instead!