01 - Place the chicken breasts between two sheets of plastic wrap and pound to an even 1/2-inch thickness using a meat mallet or rolling pin.
02 - In a mixing bowl, whisk together the buttermilk, 1 teaspoon of salt, and 1/2 teaspoon of black pepper until well 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 the all-purpose flour, cornstarch, paprika, garlic powder, cayenne pepper (if using), salt, and black pepper. Whisk until evenly distributed.
05 - Remove each chicken breast from the marinade, allowing excess buttermilk to drip off. Press each piece firmly into the flour mixture, ensuring an even and thorough coating on all sides.
06 - Pour vegetable oil into a large skillet or deep pan to a depth of about 1/2 inch. Heat over medium-high heat until the oil reaches 350°F. Use a kitchen thermometer to verify temperature.
07 - Carefully place the coated chicken breasts into the hot oil, working in batches to avoid overcrowding. Fry for 6 to 7 minutes per side until golden brown and the internal temperature registers 165°F.
08 - Transfer the fried chicken to a paper-towel-lined plate and let rest for 2 to 3 minutes to allow juices to redistribute before serving.