To make the pickles, put the vinegar and sugar in a saucepan and bring to the boil. Turn down the heat and simmer until the sugar has dissolved. Leave to cool, then mix in the carrots and cucumbers.
To make the nuoc cham, put all the ingredients in a bowl and mix well.
To make the sriracha mayonnaise, mix together the mayonnaise and sriracha.
To make the mango, put the mango on a plate and cover with the lime zest and juice, ½ teaspoon of salt and pepper to taste.
To serve, heat a large frying pan and add the oil. Once hot, add the prawns and cook for 2–3 minutes on each side, or until cooked through.
Place the pickles in the baguettes, then top with the prawns and mayonnaise. Add the nuoc cham and coriander sprigs. Serve with the mango.