Place the cottage cheese and Greek yogurt into a blender or food processor. Process on high speed for 30 seconds until the texture is completely smooth and resembles a thick dressing.
In a large stainless steel mixing bowl, combine the shredded chicken breast, diced celery, and minced red onion.
Pour the blended cottage cheese mixture over the chicken and vegetables.
Add the Dijon mustard, lemon juice, garlic powder, salt, and black pepper to the bowl.
Using a silicone spatula, fold the ingredients together until the chicken is thoroughly and evenly coated with the dressing.
Gently stir in the chopped fresh parsley.
Transfer to an airtight container and refrigerate for a minimum of 30 minutes to allow the flavors to emulsify and the proteins to chill.