First, prepare the chicken brine by combining the kosher salt and warm water in a large bowl. Whisk until all salt is completely dissolved. Pop the brine in the refrigerator until completely cooled.
When brine is cool, add the chicken and peppercorns and place in the refrigerator to brine for 30 minutes while you prep the other ingredients.
In a shallow bowl, mix breadcrumbs, grated parmesan, salt, pepper, and dried parsley.
In a separate shallow bowl, whisk together: liquid egg whites, flour, and garlic powder.
Spray the air fryer pan or basket with non-stick olive oil spray. Preheat the air fryer to 375 degrees F.
Remove the chicken from the brine and pat dry with a paper towel. Dip each chicken breast in the egg mixture, then dip in the breadcrumb mixture, making sure that each breast is coated with the breading.
Place the breaded chicken breasts in the air fryer basket or tray and spray the top thoroughly with olive oil spray, working in batches if necesary.
Cook at 375 degrees F for 5 minutes, then flip and spray the other side with olive oil spray and cook 5-7 minutes more until the chicken reaches a safe internal temperature of 165 degrees F with a meat thermometer. Cooking time will vary depending on the thickness of the chicken breasts.
Garnish with fresh parsley, if desired