In a bowl, add the buttermilk, salt, pepper and the egg whisk until well combined. Then, toss the chicken in the marinade and mix well.
After that, cover the bowl and refrigerate for at least 12 hours.
In a big plate, add the cornstarch, flour and all the spices, mix everything well. Then set aside.
Add oil to a deep pot on medium heat.
Bring the chicken from the fridge then toss each piece in the breading mixture, make sure to coat all the chicken pieces well from all sides.
Once the oil heated place the chicken carefully in the oil (the oil should be deep enough to cover it).
Fry the chicken for about 6-8 minutes until it becomes dark golden brown.
Notes
Buy small size thighs or small size whole chicken because it will fry well and more evenly.
Don't keep turning the chicken pieces on the other side while frying, so you don't separate the crust from the chicken; also the oil should be deep enough to cover the whole chicken pieces.
It is preferable to marinate the chicken for an overnight, that will make it so tender and soft.