Marinade the chicken in buttermilk mix overnight.
Drain off excess liquid, coat in the flour mix, leave for 20- 30 minutes to allow the flour to soak up.
Coat again, allow to soak up and if needed coat again, three times max.
Deep fry in 170c oil until cooked. If pieces are big you can place them on a wire rack and in the oven at 160c after deep frying to finish off.