For the red snapper, place four large pieces of aluminium foil on the work surface. Place an equal amount of lemongrass, chili, lime leaves and cilantro on each piece of foil, then place the snapper fillets on top. Pour over the lime juice and fish sauce.
Season with salt and pepper and drizzle with olive oil. Fold the aluminium foil over to encase the ingredients and seal (like a Cornish pasty). Make sure that the foil is sealed well and that there is room for steam to circulate in the package.
Heat a large ovenproof frying pan (alternatively, preheat a roasting tray in the oven) and put the parcels in the pan. Place the pan in the oven for 6 minutes.
For the mitzuna salad, place the mitzuna and rocket leaves in a bowl and add place the remaining salad ingredients into a pestle and mortar and pound to a paste. Add the paste to the bowl of leaves and toss to coat.
To serve, place the salad on serving plates with the snapper fillets. Garnish with chopped cilantro.