Place the chicken pieces in a large bowl and season them with salt, crushed garlic, hot sauce, and Creole seasoning.
Pour some of the buttermilk over the seasoned chicken (add optional cornstarch), transfer it to a large bowl or gallon-sized ziplock freezer bag, and marinate it covered in the refrigerator for at least 4 hours (or overnight).
Whisk the flour, cornstarch, baking powder, paprika, garlic powder, onion powder, herbs, cayenne pepper, white pepper, and salt in another large bowl.
Remove the marinated chicken from the buttermilk and let the excess buttermilk drain back into the bowl.
Then, dredge it in the flour mixture, shaking off excess flour. You could use a ziplock bag for this process, too.
Optional step: Double-dip the chicken in the remaining buttermilk (add fresh buttermilk as needed), then repeat with the flour mixture, shaking off the excess. Let the chicken rest for 10-15 minutes while heating the oil. That will help the coating to stay on better.
Heat oil in a deep fryer or cast-iron skillet to 375℉ (190℃). The temperature will drop once you add chicken. Optionally, fry a few pieces of onion in the oil to test the temperature and infuse more flavor.
Slowly and carefully place the chicken in the hot oil using tongs. Work in batches to avoid overcrowding the skillet.
Fry the chicken until golden brown, turning once every 10-15 minutes, depending on the thickness of the pieces. Chicken is done when it is no longer pink inside, and its juices run clear, or your instant-read thermometer reads 165℉ (75℃). You could do a test by piercing the chicken with a fork.
Drain the chicken on a rack over a baking sheet, dab with paper towels to remove excess oil if necessary.
Repeat with the remaining chicken pieces. Let them rest for at least 10 minutes before serving.