2) Add the Cajun seasoning to the prawns and let marinate for 20 minutes, while you make the chutney.
3) In a skillet, warm 1 tablespoon of olive oil over low heat, until shimmering Add the cumin and fennel, it should splutter.
4) Stir in the onion and serrano pepper and saute until softened and slightly coloured. Add the turmeric and saute for 30 seconds. Stir in the pineapple and toss to coat with the spices. Cook for about 5 minutes. Add the coriander and mayonnaise and stir to combine.
5) Add some maize meal to a shallow plate. Coat each prawn evenly with maize meal, while you warm up a few tablespoons of vegetable oil in a large skillet over medium-high heat. When oil is shimmering (hot), add the prawns in batches. Flip after 2 minutes, or when they start to change colour. Cook another 2 minutes on the other side, until cooked to your liking (don't overcook; should only take 5 minutes, tops!). Remove the prawns from the skillet to a paper towel-lined plate.
6) To build the po' boy, slather the pineapple-mayonnaise mixture on one side of each bun bottom. Spoon a generous helping of prawns over the top. Add some lettuce and tomato and cover with the bun tops. Wrap in clingfilm and aluminium foil and you're ready for the picnic!