In a large bowl, whisk together the egg, buttermilk, hot sauce and 1 tablespoon salt to make the marinade.
Add the chicken pieces to the marinade, stir to coat, cover, and refrigerate 12 to 24 hours, turning once to ensure even coating.
When ready to cook, heat vegetable oil in a heavy-bottomed pan or deep fryer to 350°F (175°C).
Line a large rimmed baking sheet with foil and set a cooling rack on top; preheat the oven to 180°F (keep warm).
In a large shallow bowl, whisk together the flour, cornstarch, black pepper, 1 tablespoon salt (for breading), garlic powder, sweet paprika, onion powder, dried thyme, dried oregano, mustard powder, celery salt, ginger powder and cayenne.
Scoop out 1/4 cup of the marinade from the chicken and drizzle it into the breading mixture; use clean fingers or a fork to mix until small lumps form.
Working one piece at a time, remove chicken from the marinade and gently shake off excess. Dredge in the breading, turning to coat completely, and press the breading onto the chicken to adhere.
Carefully add 3 to 4 pieces of coated chicken to the hot oil, leaving space between pieces. Fry without disturbing for at least 2 minutes to set the crust, flipping as needed.
Fry until the crust is deep golden brown and the internal temperature reaches 165°F, about 6 to 8 minutes depending on piece size.
Transfer fried chicken to the prepared rack-lined baking sheet and keep warm in the preheated oven while you finish frying the remaining pieces.
Serve warm and enjoy.
