In a bowl, add potato starch, cake flour, salt and whisk together. Then pour in water and whisk again until combined. Set aside.
In another bowl, whisk together Mayo sauce ingredients (see listed above) until well combined. Set aside.
If needed, peel and devein shrimp. Pat the peeled shrimp dry and add shrimp to batter. Mix together.
In a large wok or pot set over medium heat, add vegetable oil. Make sure oil reaches 350 F or dip a wooden chopstick and look for bubbles at the tip. Once the oil is hot, carefully add half of the battered shrimp. Do not overcrowd the oil.
Fry shrimp until they float and are pink through out, about 2-3 minutes. Flip shrimp halfway through frying. If you’d like them extra crispy, drizzle a teaspoon of the batter per each piece of shrimp as it fries (optional).
Remove the shrimp and place onto cooling rack to allow excess oil to drip off. If you don’t own a cooling rack, place fried shrimp on a plate lined with paper towel. Repeat the above process for second batch.
Pour the mayo sauce over fried shrimp and gently mix. Optional: garnish with dried parsley flakes. Enjoy!