Cut the chicken thigh into medium bite-size pieces. Marinade the chicken pieces with soy sauce, Shao Xing wine, garlic paste, white pepper and Chinese five spices. Mix well and set it aside for 15 minutes. Or you can leave it overnight in fridge with air-tight container.
Finely grind the roasted Sichuan peppercorns and mix it with white pepper powder, salt and paprika powder. Set it aside.
Break one egg white into the marinated chicken pieces and mix it well.
Place the sweet potato flour/ potato starch in a large bowl. Add 3-4 chicken pieces in the flour, dredge and press gently to coat evenly. Toss the excess flour out before frying.
Heat the vegetable oil or neutral flavour oil to medium-high heat about 320-330°F. ( Fill the oil over 2 inch. )
Add the coated chicken pieces and fry for 2-3 minutes. Once the chicken pieces start to float remove from oil and set aside for 2-3 minutes. ( Fry with batches if needed, do not overcrowd the oil. Skim the fried crumbs out with mesh strainer after frying each batch. )
Place the fried chicken back in the oil and fry for another 2-3 minutes, or until the coating is crispy. Remove from oil and transfer to kitchen towel or cooling rack.
Fry the basil leaves in the remaining oil for 1-2 minutes until crispy. Place the fried basil leaves over the kitchen towel.
Mix fried chicken pieces and basil leaves, sprinkle the salt seasoning mix on top. ( Or you can toss everything in a large mixing bowl. )
Transfer to serving plate and serve immediately.