Preheat a baking sheet in the oven to 200C/400F/Gas 6.
Place all the ingredients into a bowl, mix together and season well with salt and freshly ground black pepper.
Place a large sheet of greaseproof paper on top of an equal-sized sheet of aluminium foil.
Pour the mixture onto one side of the paper, arranging the prawns on top.
Fold the paper in half and seal the edges by rolling up tight.
Carefully place the sealed bag on the baking tray and bake for about 15 minutes
To serve, transfer the bag onto a plate and tear open at the table.
