Start by making the remoulade sauce. In a small bowl, combine the mayonnaise, Dijon mustard, pickle relish, minced garlic, lemon juice, hot sauce, and season with salt and black pepper to taste. Mix well, cover, and refrigerate until needed.
Prepare the prawn filling. In a shallow dish, combine the flour, paprika, cayenne pepper, salt, and black pepper. In another dish, whisk the eggs. Place the breadcrumbs in a third dish.
Heat about 2-3 cm of vegetable oil in a deep frying pan or skillet over medium-high heat until it reaches 180°C.
Dredge each prawn in the seasoned flour, then dip it into the beaten eggs, and finally coat it with breadcrumbs. Make sure each prawn is well-coated.
Carefully place the breaded prawns into the hot oil, making sure not to overcrowd the pan. Fry for about 2-3 minutes per side, or until they are golden brown and crispy. Remove them with a slotted spoon and place them on a paper towel-lined plate to drain any excess oil.
Slice the baguettes or sub rolls in half lengthwise, but not all the way through. Toast them in a hot oven for a few minutes until they are slightly crispy.
To assemble the sandwiches, spread a generous amount of remoulade sauce on the inside of each baguette or roll.
Arrange the crispy prawns on the bottom half of the baguette. Top with tomato slices, dill pickle slices, and torn iceberg lettuce.
Close the sandwich with the top half of the baguette, and secure it with toothpicks if needed.
Serve your delicious Prawn Po' Boy sandwiches immediately with extra remoulade sauce on the side for dipping.