01 - Place 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 buttermilk, 1 teaspoon salt, and 1/2 teaspoon black pepper. Submerge the chicken breasts in the marinade, cover, and refrigerate for at least 30 minutes or up to 4 hours for maximum tenderness.
03 - In a separate shallow bowl or dish, combine flour, cornstarch, paprika, garlic powder, cayenne pepper (if using), remaining 1 teaspoon salt, and 1/2 teaspoon black pepper. Mix thoroughly to distribute seasonings evenly.
04 - Remove each chicken breast from the buttermilk marinade, allowing excess liquid to drain off. Press each piece firmly into the seasoned flour mixture, ensuring full coverage on all sides. Shake off any loose coating.
05 - 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, monitoring with a kitchen thermometer for accuracy.
06 - Carefully place dredged chicken breasts into the hot oil in batches, avoiding overcrowding. Fry for 6 to 7 minutes per side until deep golden brown and the internal temperature registers 165°F at the thickest part.
07 - Transfer the fried chicken to a paper-towel-lined plate or wire rack. Allow to rest for 2 to 3 minutes so juices redistribute before serving.