In a large bowl, soak chicken pieces in buttermilk for at least 30 minutes, or overnight for best results.
In a separate bowl, combine all-purpose flour, cornstarch, paprika, garlic powder, onion powder, cayenne pepper, salt, and black pepper.
Heat vegetable oil in a deep fryer or large skillet to 350°F (175°C).
Dredge each chicken piece in the flour mixture, shaking off excess.
Carefully place chicken in the hot oil, working in batches to avoid overcrowding the fryer.
Fry chicken for 12-15 minutes, or until golden brown and crispy, turning occasionally for even cooking.