In a medium sized mixing bowl combine 1.25cups/300ml buttermilk with 1 tsp salt and 1/2 tsp paprika, cayenne pepper, onion powder, garlic powder & white pepper. Add in potatoes and stir with a spatula to completely coat. Leave to marinate in the fridge for AT LEAST 30mins, the longer the better though (up to 3 hours).
Meanwhile in a large bowl combine 1.5cups/225g flour with 2 tsp paprika, 1 tsp baking powder, salt, oregano, onion powder & garlic powder, 1/4-1/2 tsp cayenne pepper and 1/4 tsp black pepper. Scoop out 3 tbsp of the marinade and stir into the flour until lots of little lumps form. This will give you those flaky/crunchy parts.
One by one, thoroughly coat the potatoes in the flour. You really need to press the flour into the potato and use the excess buttermilk to form those flaky bits. That's what will give you the crunch. Place on a wire rack to one side and repeat with remaining potatoes.
Heat up 3-4cups/750ml-1litre vegetable oil in a large deep pot to 175C/350F. In batches, use a slotted spoon to gently lower the potatoes into the oil. Immediately separate them if they begin to stick, then leave to fry for 7-8mins or until golden and crispy. Timings will depend on size and thickness of potato, how long you marinated for and how much flour attached, so just be vigilant (they will continue cooking slightly as they rest). Remove and place on wire rack with paper towels underneath (don't add straight to paper towels or you run the risk of the outside steaming/going soggy). Repeat with rest of potatoes.
Once they're fried, sprinkle both sides with a little salt. This is essential not only to season and bring out the flavours, but it'll also draw out the final bits of moisture from the batter. Serve with you favourite dip (suggestions in notes).