Grab a large bowl and whisk together the buttermilk, egg, salt, and hot sauce until fully combined. This mixture is what makes the chicken tender and flavorful all the way through. Make sure the egg is fully incorporated so the marinade coats evenly.
Place the chicken breasts into the marinade, making sure each piece is fully submerged. Cover the bowl and refrigerate for at least one hour, though I often let mine sit longer. This resting time is what gives the chicken its signature juicy texture.
While the chicken marinates, pour at least two inches of oil into a large, heavy pot. Heat it to exactly 350°F using a deep-fry thermometer to check. Getting this temperature right is key so the outside doesn't burn before the inside cooks through.
In a separate bowl, whisk together the flour, salt, white pepper, celery salt, granulated garlic, and paprika. This blend is what gives the crust its bold, savory flavor. Stir it well so every spice is evenly distributed throughout the flour.
Lift each chicken breast out of the buttermilk, letting the excess drip off before pressing it into the seasoned flour. Coat every side thoroughly, pressing gently so the flour sticks well. A good, even coating is what creates that satisfying crunch.
Carefully lower the coated chicken into the hot oil, frying for 15-20 minutes and flipping occasionally. I never crowd the pot, frying just two pieces at a time so the oil stays hot. Check that the internal temperature reaches at least 165°F before removing.
Transfer the fried chicken to a wire rack or plate lined with paper towels to soak up extra oil. Blotting it this way keeps the crust crisp instead of soggy. Finish with a sprinkle of fresh parsley before serving.