Trim fennel leaves and blanch bulb in boiling water for a few minutes. Remove the zest from the lemon.
Using a pestle and mortar crush the herbs, add the olive oil to make a paste, cut lemon in half and add the juice and mix. Set to one side.
Remove the skin from fish if you prefer, lightly salt and spread enough of the paste to cover the whole of the fillet.
Place fillets on a greased piece of foil large enough to make a parcel.
Place parcels on a baking tray and place in the oven on the top shelf.
Bake for 20 to 30 minutes, making sure the sea bass is cooked but do not overcook.
Meanwhile, prepare the salad by cutting oranges into segments, slicing salad leaves and chopping fennel leaves.
Slice fennel bulb into very thin slices.
Using a mixing bowl, place the cooked prawns, salad leaves, fennel slices and orange into it, add a few drops of olive oil and lemon zest then toss.
To serve, place a large handful of salad on a plate, carefully remove fish from parcel and place on top of the salad. Sprinkle with chopped fennel leaves and squeeze the other half of the lemon over the fish.