Add the chicken pieces, buttermilk, salt, and pepper to a medium bowl. Marinate for at least 30 minutes.
Place the cornstarch in a small bowl and set aside.
Whisk the eggs with a fork in a separate bowl and set aside.
Add the flour, garlic powder, onion powder, paprika, salt, and pepper to a plate. Mix well and set aside.
Dredge each piece of marinated chicken in the cornstarch, dip it into the egg mixture, then coat it with the seasoned flour. Shake off any excess flour.
Repeat with the remaining chicken pieces and place them on the prepared baking sheet.
Preheat the air fryer to 390°F. Spray the air fryer basket with cooking spray.
Place the chicken pieces in a single layer in the air fryer basket. Spray the tops with cooking spray.
Air fry for 10-12 minutes, flipping the chicken halfway through, until crispy, golden, and completely cooked through.
Garnish the popcorn chicken with fresh parsley and serve with ranch or ketchup.