1. Heat oil in a 12-inch stainless lidded skillet (cast iron, if desired) over medium heat to 350 degrees F on a deep-fry thermometer. Oil should be 1 1/2 to 2 inches deep. Heat oven to 200 degrees F.
2. In a medium bowl, whisk together buttermilk and egg. In a second bowl or shallow dish, combine flour, garlic salt, onion powder, black pepper, baking soda and cayenne.
3. Pat chicken dry. Coat a few of the chicken pieces with flour mixture. Dip in buttermilk mixture, allowing excess to drip back into the bowl. Return to flour mixture to coat. Place on a wire rack over a baking sheet while you coat remaining chicken pieces.
4. Carefully place 4 to 5 pieces of chicken skin-side down in hot oil (don't let pieces touch). Fry 4 minutes. Flip pieces over with tongs and fry 4 more minutes. Try to keep temperature around 350 degrees F; you will have to adjust heat under pan. Flip chicken one more time and cover pan. Cook 4 to 5 more minutes or until pieces register 165 degrees F on an instant-read thermometer. Transfer to a baking pan fitted with a wire rack and keep warm in 200 degrees F oven. Repeat with all chicken pieces.