Marinate the chicken in the soy sauce, Shaoxing wine, garlic, five spice, white pepper, and sugar for at least 15 minutes, or up to overnight in the fridge.
Stir the beaten egg into the marinated chicken. Spread the sweet potato starch on a plate and roll the pieces through it a few at a time, pressing so the coarse granules stick. Let the coated pieces rest 5 minutes so the starch hydrates and stops looking dusty.
Spray the air fryer basket with oil, add the chicken in a single layer, and spray the tops generously. Any dry white patches of starch will stay pale and chalky, so hit them all.
Air fry at 200C (400F) for 10 to 12 minutes, turning the pieces halfway and spraying again, until deep golden and crunchy. Work in two batches; a crowded basket steams.
Toss the basil leaves with a tiny spray of oil and air fry them on top of the last batch for the final 2 minutes until translucent and crisp.
Tip everything into a bowl, dust with the extra five spice, white pepper, and salt while hot, and toss with the crispy basil. Eat immediately.