For the chips: In a bowl mix the potato slices, cajun, oil, and season well with salt. Spread out on parchment paper lined baking sheet(s). Avoid overlapping the potato slices. Place in the oven and cook to golden brown and crisp on both sides. Remove from the oven and season with salt to taste.
For the shrimp: Heat the oil in a saucepan to 350 degrees. In a bowl mix together the flour, eggs, baking powder, and old bay. Stir in water a little at a time until a thick batter forms. Dip the shrimp into the batter and fry (in batches if needed) golden brown and crispy to an internal temperature of 125 degrees using a thermometer.
For the remoulade: whisk together all ingredients in a bowl. Adjust any of the ingredients to taste.
Serve the shrimp with chips and remoulade. Garnish with parsley