Take chicken out of the fridge and drain away any excess liquid, then gently pat dry. Add the flour, cornstarch, baking powder and five spice powder to a bowl, then slowly drizzle in a little water while mixing until the batter can form a thin, unbroken stream when drizzled from a spoon. In a separate shallow dish, sift together the sweet potato starch and the sticky rice flour.
Bring the oil up to 300℉ in a wok or deep fryer. Using separate tongs for the wet batter and the starch, and working as neatly as possible, roll the chicken pieces in batter and then in the starch mixture, then put them in the oil. Work in batches, making sure not to add the pieces too fast or crowd the pot, or the oil temperature will drop too much. Fry each batch for about five minutes, or until the surface of each piece of chicken reaches a pale yellow color. Remove the chicken with a strainer and set the pieces on a rack.
When all the chicken has been fried once, bring the oil up to 400℉ degrees, then add chicken pieces back to the oil, in batches, frying for another minute or so to add color and crisp everything up. Once the chicken takes on a bronze hue, remove it from oil and set on a rack to let excess oil drain.
When all the chicken is fried, add basil leaves to the oil (if using) and fry until they’re twisted and shatteringly crispy. Lightly toss the fried chicken in a bowl with the fried basil and a sprinkling of white pepper. For the best experience, serve the chicken hot in a parchment-lined basket with skewers or toothpicks.