In years past, shrimp were a really inexpensive ingredient in Louisiana, and so became traditional in the legendary ‘poor boy’ sandwiches. Much more of a treat today, these crisp and spicy fried prawns make for a pretty luxurious snack.
For the Cajun seasoning, place all the ingredients in a large bowl and mix together thoroughly. In a separate bowl, stir together the mayonnaise, parsley and gherkins. Stir through 2 teaspoons of Cajun seasoning, or to taste, and set aside. Stir the flour through the remaining Cajun seasoning.
In another bowl, beat together the egg and milk. Line up the prawns, the flour/spice mix, egg and milk mix, and a large clean plate on the worktop. Take a prawn and dip it into the flour to coat all over, then dip into the egg and milk, then back into the flour for a second coating, before setting aside on the plate. Repeat until all the prawns have a double coating of spicy flour.
Heat the oil in a deep fat fryer to 180°C/350°F and fry the prawns in batches for about 3 minutes until golden and crisp. Drain briefly on kitchen paper. To serve, slice the baguettes through, but leave top and bottom hinged together. If you like you can warm them briefly in a hot oven. Spread a little mayonnaise dressing inside each piece of bread and add some lettuce and tomato slices. Top with the crisp prawns and a further dollop of dressing and tuck in while hot.