01 - Place chicken breasts between two sheets of plastic wrap and pound to an even thickness of about 1/2 inch using a meat mallet.
02 - In a mixing bowl, whisk together buttermilk, 1 teaspoon salt, and 1/2 teaspoon black pepper until combined.
03 - Submerge the pounded chicken breasts in the buttermilk mixture. Cover and refrigerate for at least 30 minutes, or up to 4 hours for optimal tenderness.
04 - In a separate shallow bowl or dish, combine flour, cornstarch, paprika, garlic powder, cayenne pepper (if using), salt, and black pepper. Whisk until evenly blended.
05 - Remove chicken from the marinade, allowing excess liquid to drip off. Press each breast firmly into the flour mixture, coating both sides thoroughly. Shake off any excess.
06 - Pour vegetable oil into a large skillet or deep pan to a depth of about 1/2 inch. Heat over medium-high heat to 350°F. Use a kitchen thermometer to monitor temperature.
07 - Carefully place chicken breasts into the hot oil in batches, avoiding overcrowding. Fry for 6 to 7 minutes per side until golden brown and the internal temperature reaches 165°F.
08 - Transfer fried chicken to a paper-towel-lined plate and let rest for 2 to 3 minutes to allow juices to redistribute before serving.