Grab two rimmed baking sheets and place a wire cooling rack onto each of them. One will be used for the raw chicken and one will be used for the cooked chicken. Set aside.
On a large plate, mix together flour, cornstarch, powdered sugar, salt, pepper, optional cayenne, dry ranch mix, and taco seasoning until well combined. Set aside.
Whisk together egg and 1/2 cup of the marinade in a deep bowl (deep enough to submerge chicken) until well combined.
Drain and discard the remaining marinade from the chicken.
Take one piece of chicken and fully coat it with breading mixture. Shake off any excess.
Place it into the egg wash bowl and fully coat, allowing excess to drip off.
Coat chicken in breading mixture, then egg wash, and then breading one more time.
Place the chicken onto one of the prepared racks. Repeat with remaining chicken.
Let chicken dry for about 15 minutes while you prepare your oil.