For the prawns, pound the coriander and olive oil together in a pestle and mortar until the mixture is the consistency of pesto. Dip the prawns in the coriander to coat.
Unravel the pastry onto a flat, clean work surface. Cut the pastry into 12 equal pieces about 10cm/4in (keep the pastry pieces covered after you've cut them out to prevent them from drying out). Wrap the pastry pieces around the prawns.
Heat a deep fat fryer to 170C/325F/Gas 3, or until a breadcrumb sizzles and turns brown when dropped into it. (CAUTION: hot oil can be dangerous. Do not leave unattended.)
Deep fry the prawns in batches until golden-brown. Remove with a slotted spoon, drain on kitchen paper and keep in a warm place until ready to serve.
For the salsa, combine all of the salsa ingredients. Leave to stand for about 15 minutes to let the flavours infuse before serving.