Whisk together the 1 cup (240ml) buttermilk and 1 large egg in a large bowl. Add the 4 chicken pieces, coat them fully, cover, and refrigerate for at least 1 hour and up to 8 hours.

In a shallow dish, whisk together the 1 cup (120g) flour, 2 tbsp cornstarch, 1 tsp salt, 1 tsp black pepper, 1 tsp white pepper, 1 tsp paprika, 1 tsp garlic powder, 1 tsp onion powder, 1/2 tsp thyme, 1/2 tsp basil, 1/2 tsp oregano, 1/4 tsp celery salt, and 1/4 tsp ground ginger. Lift each chicken piece from the buttermilk, let the excess drip off, then press firmly into the flour blend on all sides. Set on a rack.

Preheat the air fryer to 380°F (195°C). Arrange chicken in a single layer, spray generously with cooking spray, and air fry for 25 minutes, flipping once at 13 minutes and spraying the second side. Cook until the internal temperature reaches 165°F (74°C).

Transfer to a serving plate, sprinkle with a pinch of salt and a few cracks of black pepper, and serve immediately.