Lay a piece of chicken on the chopping board and cover with a sheet of cling film. Pound with a rolling pin, mallet or even a heavy pan. You want it fairly thin, but not so thin it starts breaking apart. The main goal is to achieve even thickness across the meat. If you're using breast you'll likely need to trim off the tail or around the outside - it should be a little larger than the bun (they shrink in size as they fry). Repeat with the rest of the chicken.
In a large mixing bowl combine 1 1/4cups/300ml buttermilk with 1 tsp paprika & salt and 1/2 tsp onion powder, garlic powder, cayenne pepper & white pepper. Place in the chicken, use tongs to fully coat then tightly cover with cling film and marinate in the fridge. I highly recommend a minimum of 4 hours (up to overnight), but just as long as you have time for. Take the chicken out of the fridge 30mins before needed to bring it close to room temp (see notes).
In a large shallow bowl (or curved tray) combine 1 3/4cups/250g flour with 2 tsp paprika, 1 tsp oregano, baking powder & salt, 1/2 tsp onion powder, garlic powder, black pepper & cayenne pepper. One by one coat the chicken in the flour, making sure you press the flour into the chicken to create lots of craggy bits. Really get in all the cracks and crevices of the chicken (this is an important step). Place on a tray to one side.
In a large pot or deep pan heat up the oil to 180C/356F. In batches of 1-2 (depending on pot size), carefully place your chicken in the hot oil. The temp will likely drop, and that's fine, but make sure the temp stays at around 165C/300F as the chicken fries. Depending on the size and thickness of the chicken, you're looking at around 6-7 minutes for thigh and 5-6 minutes for breast, flipping halfway. The internal temp of the chicken should reach 75C/165F. Carefully remove and rest on a wire rack with paper towels underneath (don't place directly on paper towel or they'll lose crispiness). Bring oil temp back up to 180C/356F between each batch.
Stack burgers in the following order: bottom bun, coleslaw, chicken, bacon, honey sriracha, top bun. Enjoy!