Season raw chicken pieces on all sides with 1 tsp seasoned salt and 1/2 tsp black pepper. Place into an oblong baking dish or large bowl and cover with 2 1/2 cups buttermilk. Turn to coat. Chill overnight, turning once.
30 Minutes Before Frying: Remove chicken from buttermilk marinade, discarding the marinade.
On a plate or shallow dish use a whisk to sift together the flour, cornstarch, 2 tsp seasoned salt, 1 tsp black pepper, garlic powder, onion powder and paprika.
In a large shallow bowl whisk together the eggs, 1/2 tsp seasoned salt, 1/2 tsp black pepper, 1/2 cup buttermilk and hot sauce.
Dredge chicken pieces first in flour then into the egg wash, then back into the flour mixture again. Gently shake off any excess.
Arrange on a baking sheet. Let stand for 30 minutes to bring to room temperature and set the breading.
Frying Chicken: Preheat the oven to 200°F. Prepare a rimmed baking sheet with an oven safe wire rack. Set aside.
Fill a 12-inch cast iron skillet about 1/3 full with oil fitted with a fry thermometer. Heat to 350°F. Carefully lower chicken pieces into the oil.
Maintain oil temperature around 350°F. Fry chicken in batches cooking dark meat pieces and white meat separately. Cook for 10-15 minutes per side or until juices run clear and the internal temperature reaches 165°F with an instant read thermometer. Turn carefully using tongs to avoid splatters.
Place chicken pieces onto the prepared pan to drain excess oil. Keep warm in the oven between batches.
Rest for 10 minutes before serving.