Rinse and pat dry the sliced potatoes.
Combine flour, cornstarch, parsley, garlic powder, onion powder, Cajun seasoning, salt, and black pepper in a bowl.
Gradually add water to achieve a thick batter consistency.
Mix well until smooth.
Coat potato slices evenly with the batter.
Heat oil in a deep frying pan to 350°F (180°C).
Fry potato slices in batches until golden brown (4 -5 minutes).
Drain excess oil on a cooling rack.
Whisk together mayonnaise, ketchup, Dijon mustard, hot sauce, garlic powder, onion powder, red chili flakes, salt, and black pepper in a separate bowl.
Mix until smooth.
Serve crispy potatoes with signature fry sauce for dipping.
