Place flour, cornstarch, garlic powder, coriander, salt and cayenne in a bowl and mix together thoroughly and set aside.
Whisk together the egg and buttermilk and set aside.
Place dried chicken, the flour mixture and egg mixture, and the wire rack and tray on a clear work surface, creating an assembly line in that order.
Douse each piece of chicken in the flour mixture, then egg mixture, and then again into the flour mixture, then place that coated piece of chicken on the wire rack, to allow the excess coating to drip or fall away.
Repeat until you have coated each piece of chicken.
Transfer coated chicken to another tray or plate and once again rinse and dry the wire rack and tray.
Pour oil into skillet, place the thermometer into the oil and heat until 350 degrees.
Carefully place pieces of chicken into the oil. You will likely have to cook the chicken in two or three batches.
Watch the thermometer, you want the oil to stay at 350 throughout the cooking process. Turn the heat up and down accordingly.
Remove each piece of chicken as soon as the coating turns a light golden color and place on wire rack.
Once every piece of chicken has been fried, place the tray of chicken into a preheated oven at 350 and allow to cook for approx. 10 mins
Test a thicker piece of chicken to make sure it's cooked through. If necessary return to the oven for a further 5 mins, or until the chicken is cooked through.
Once done, allow chicken to rest for 5 minutes before serving.