Marinate the Chicken: In a bowl, mix buttermilk, salt, black pepper, garlic powder, onion powder, and paprika. Submerge chicken pieces, cover, and refrigerate for at least 4 hours (overnight for best results).
Prepare the Coating: In a shallow dish, combine flour, cornstarch, salt, black pepper, paprika, cayenne pepper, oregano, and baking powder.
Coat the Chicken: Remove chicken from buttermilk, letting excess drip off. Dredge in the flour mixture, pressing to coat. For extra crispiness, dip again in buttermilk and coat with flour.
Heat the Oil: Heat oil in a deep fryer or heavy-bottomed pot to 350°F (175°C).
Fry the Chicken: Fry in batches, ensuring oil temperature stays consistent. Cook for 12–15 minutes, turning occasionally until golden brown and crispy.
Drain and Rest: Transfer to a wire rack to drain excess oil and let rest for 5 minutes before serving.