01 - Place the chicken breasts between two sheets of plastic wrap and pound them to an even thickness of about 1/2 inch using a meat mallet or rolling pin.
02 - In a mixing bowl, combine the buttermilk, 1 teaspoon of salt, and 1/2 teaspoon of black pepper. Add the pounded chicken breasts, ensuring they are fully submerged, and marinate for at least 30 minutes or up to 4 hours in the refrigerator for optimal tenderness.
03 - In a separate bowl, whisk together the all-purpose flour, cornstarch, paprika, garlic powder, cayenne pepper (if using), 1 teaspoon of salt, and 1/2 teaspoon of ground black pepper until evenly combined.
04 - Remove the chicken from the buttermilk marinade, allowing any excess to drain off. Dredge each breast in the seasoned flour mixture, pressing firmly to ensure the coating adheres well on all sides.
05 - In a large skillet or deep pan, heat about 2 cups of vegetable oil to 350°F (175°C). Use a kitchen thermometer to verify the temperature for consistent results.
06 - Carefully lower the coated chicken breasts into the hot oil in batches, avoiding overcrowding. Fry for 6 to 7 minutes per side until the exterior is golden brown and the internal temperature reaches 165°F (74°C).
07 - Transfer the fried chicken breasts to a paper-towel-lined plate to drain excess oil. Allow to rest for 2 to 3 minutes before serving.