oss the prawns with the garlic, chilli flakes and oil, cover with clingfilm and refrigerate for 1 to 2 hours, or overnight if possible. Meanwhile, make the salsa. Preheat the barbecue to a high heat, lay the tomatoes, chillies and spring onions on the grill and cook for 3 to 4 minutes until charred and starting to soften.
Remove from the grill and transfer to a chopping board. Roughly chop everything together then tip into a liquidiser and add the remaining ingredients. Pulse to a rough purée then season to taste and set aside. Meanwhile remove the prawns from the fridge and bring to room temperature. Lay the prawns on the grill and cook for 1 to 2 minutes on each side until pink. Transfer to a platter and serve with the salsa and lime wedges.