Heat the vegetable oil to 325 degrees Fahrenheit.
While the oil is heating, put the breadcrumbs in a bowl. In a separate bowl, whisk the eggs, buttermilk, and hot sauce together. In another bowl, whisk together the flour, cornstarch, cayenne powder, garlic powder, onion powder, salt, and pepper until well combined.
Add one shrimp to the flour mixture and coat completely before removingit and tapping off the excess flour.
Then, stick the shrimp with a fork and dip it into the egg mixture, but don’t let it sit for more than five to six seconds before draining the excess egg off.
Lastly, dredge the shrimp in the breadcrumbs and toss the excess off before carefully dropping them into the hot oil. Add only five shrimp at a time so that the oil doesn’t cool down.
Let them fry on one side for about three minutes before turning and frying on the other side for a minute or two, or until the shrimp turns a light brown or tan color on both sides.
Remove the shrimp from the oil and let drain over a cooling rack or on a plate with a paper towel.
Assemble the po'boy by adding shredded lettuce to the bun first, then tomato slices, then onions, then shrimp, and finally the remoulade sauce.
To make the remoulade sauce, whisk all of the ingredients and season with salt and pepper.