01 - Place chicken breasts between two sheets of plastic wrap and gently pound with a meat mallet to an even 1/2-inch thickness throughout.
02 - Whisk together the buttermilk, kosher salt, black pepper, and garlic powder in a shallow bowl until well combined.
03 - Submerge the pounded chicken breasts in the buttermilk mixture, turning to coat evenly. Cover and refrigerate for at least 30 minutes, or up to overnight for deeper flavor penetration.
04 - In a separate shallow dish, combine the all-purpose flour, smoked paprika, cayenne pepper, onion powder, kosher salt, and black pepper. Whisk until uniformly blended.
05 - Pour vegetable oil into a large skillet or deep frying pan to a depth of about 1/2 inch. Heat over medium-high heat until the oil reaches 350°F. Use a thermometer to monitor the temperature.
06 - Remove each breast from the buttermilk marinade, allowing excess liquid to drip off. Dredge thoroughly in the seasoned flour mixture, pressing firmly on both sides to ensure the coating adheres completely.
07 - Carefully lower the breaded chicken into the hot oil, working in batches to avoid overcrowding. Fry for 6 to 7 minutes per side until the exterior is deep golden brown and the internal temperature registers 165°F on an instant-read thermometer.
08 - Transfer the fried chicken to a wire rack set over a sheet pan or a paper towel-lined plate to drain excess oil. Allow the chicken to rest for 5 minutes before serving to let juices redistribute.