Place the chicken breast in a shallow dish and pour the buttermilk over it, ensuring it is fully coated; marinate for at least 30 minutes in the refrigerator.
In a small bowl, whisk together 2 tablespoons of whole wheat flour, garlic powder, onion powder, smoked paprika, sea salt, and black pepper.
Remove the chicken from the buttermilk, letting the excess drip off, then dredge it thoroughly in the seasoned flour mixture until coated.
Lightly brush or spray the air fryer basket with the avocado oil, place the chicken inside, and cook at 375°F for 12-15 minutes, flipping halfway through.
While the chicken cooks, whisk the remaining 1 tablespoon of flour and chicken broth in a small saucepan over medium heat until thickened.
Stir the milk and fresh parsley into the saucepan, simmering for 1 minute until the gravy is smooth and creamy.
Plate the crispy chicken and pour the warm gravy over the top before serving immediately.