Put the chicken pieces in a large bowl and cover them with about 2 cups of buttermilk, add 2 tablespoons of salt, and 2 tablespoons of sugar.
Cover the bowl, and refrigerate for 8 overnight. When you soak the chicken overnight in a buttermilk, salt, and sugar, brine, the flavor infuses into the chicken meat and makes it so tender, juicy. and flavorful.
Before frying drain off brine and place on a platter till the oil is ready.
Pour oil into a deep-frying pan or deep cast iron skillet to a 1-inch depth and heat the oil to about 375 degrees F. Check the temperature by sprinkling a little of the flour over the oil. If the flour sizzles well, the oil is hot enough.
Drain the brine off of the chicken, sprinkle each piece with some kosher salt and fresh ground pepper, and coat the pieces with flour mixture, by placing the flour, cornstarch, kosher salt, Cajun seasoning, ground black pepper, garlic powder, and paprika in a brown paper sack, closing the top and gently shaking the chicken till evenly coated in breading, shaking off any of the excess.
Carefully place the chicken in the hot oil. Place the lid on the pan, leaving an opening for the steam to escape. Cook for about 10 minutes.
Remove the lid and, using tongs, gently turn each piece of chicken careful not to burn yourself.
Replace the lid and cook for 10 minutes more, or until done, be sure to leave a small opening.
Remove the lid, turn the chicken cook for about 5 minutes uncovered, then turn again and cook another 5 minutes uncovered.
Drain the chicken on a baker rack with a metal sheet pan below for about 4-5 minutes.