Place the chicken pieces in a container, cover with the buttermilk and refrigerate for 12 hours.
Preheat the oven to 180C/375F/Gas 4.
Mix together the flours with the dried spices and herbs on a large plate. Remove the chicken from the buttermilk and shake off as much of the buttermilk as possible. Roll the chicken pieces around in the dry mix until coated.
Heat a large frying pan over a medium-low heat and add a glug of oil. Fry 2-3 pieces of chicken at a time (do not crowd the pan) until golden-brown all over and cooked through. When cooked, drain the chicken on kitchen paper and then transfer to a roasting tin.
Put the chicken pieces in the oven until the coating is crunchy rather than crisp (up to 15 minutes).