a crinkle cutter or a mandoline with a crinkle blade
Using a crinkle cutter or mandoline with a crinkle blade, carefully slice the potatoes 1/4 inch thick, rotating the potatoes 90 degrees between each cut. This will create the waffle appearance. Place the potatoes in a large bowl and cover with cold water. Cover and place in the fridge for 1 hour.
Mix the seasoning salt, paprika, pepper, garlic powder, onion powder and cayenne in a small bowl and set aside.
Remove the potatoes from the fridge and drain. Transfer to a baking sheet and pat dry with paper towels.
Heat a few inches of vegetable oil to 260 degrees F in a large heavy pot. Fry the potatoes in one batch for about 2 minutes, or until soft. They should not be brown at all at this point; you just want to start the cooking process. Remove and drain them on new, dry paper towels.
Turn up the heat until the oil reaches 325 degrees F. Return the potatoes to the oil and fry until golden and crisp, about 3 minutes. Remove the fries from the oil and drain on fresh paper towels. Sprinkle with the seasoning mix, toss to coat and serve with ketchup or sour cream dip.