Place the pieces of fish on individual rectangles of parchment paper with the foil rectangle underneath.
Squeeze the limes and add the soya sauce and sweet chilli sauce and whisk to mix.
Cut the pepper, courgettes and leeks into gougons and place on top of each piece of fish.
Pour the marinade over each parcel and bring the edges of the foil and parchment paper together to form a parcel.
Cook for 12 minutes at 180°C/350°F/Gas mark 4