Place the chicken pieces in a large bowl, pour the buttermilk and barbeque sauce on top. Season with salt and pepper; keep aside for at least 2 hours or overnight as time permits.
Preheat the oven to 250°C. Line a tray with baking paper and lightly brush or spray with vegetable oil.
In a bowl, mix the cornflakes, Panko crumbs, flour, cayenne, red chilli, paprika, onion powder, garlic powder and season with salt and pepper.
Remove each piece of chicken from the buttermilk and coat with the cornflakes mixture. Press gently so that the crumb adheres to the chicken and place it on the baking tray. Repeat for all pieces. Make sure that you do not crowd the tray; if necessary, prepare in batches or on 2 trays.
Lightly spray or drizzle the chicken pieces with oil and bake for 10-12 minutes at 250°C. Then decrease the heat to 200°C and bake for another 10-12 minutes. Keep an eye on the chicken and take care it does not burn.
Flip the chicken pieces over gently, lightly spray or brush with oil and bake again at 200°C for another 15-20 minutes or till done. Check after 10 minutes to see if any pieces are done (the wings may cook faster than the breast pieces) and remove if necessary.