Marinate Chicken: In a bowl, combine the bite-sized chicken pieces with soy sauce, Shaoxing wine, five-spice powder, white pepper, sugar, minced garlic, and grated ginger. Mix well, cover, and refrigerate for at least 30 minutes, or up to 2 hours for best flavor.

Prepare Batter: In a separate bowl, whisk the egg. Add the sweet potato starch to a shallow dish.

Coat Chicken: Dip each marinated chicken piece into the whisked egg, allowing excess to drip off, then dredge thoroughly in the sweet potato starch, pressing lightly to ensure an even coating. Set aside on a plate.

Heat Oil: Heat the vegetable oil in a deep pot or wok to 350°F (175°C). Ensure you have enough oil for the chicken pieces to be fully submerged.

First Fry Chicken: Carefully add a batch of coated chicken pieces to the hot oil, being careful not to overcrowd the pot. Fry for 3-4 minutes, or until light golden brown and cooked through. Remove with a slotted spoon and place on a wire rack set over paper towels to drain. Repeat with remaining chicken.

Fry Thai Basil: Increase the oil temperature to 375°F (190°C). Carefully add the fresh Thai basil leaves to the hot oil and fry for about 10-15 seconds, or until crispy. They will crisp up very quickly. Remove immediately with a slotted spoon and drain on paper towels.

Second Fry Chicken (Optional for Extra Crispiness): For an extra crispy texture, return all the pre-fried chicken to the hot oil (375°F/190°C) and fry for another 1-2 minutes until deeply golden brown and very crisp. Remove and drain again.

Season and Serve: Transfer the crispy chicken to a serving bowl. Sprinkle generously with salt and white pepper, and optional chili powder. Toss with the crispy fried Thai basil leaves. Serve immediately as a delicious snack or appetizer.