Preheat the oven to 200C/400F/Gas 6.
For the sea bass en papillote, place the sea bass fillet onto a square of greaseproof paper twice the size of the sea bass fillet. Place onto a baking sheet.
Add the cubed butter, salt and freshly ground black pepper, lemon juice and white wine and pull up the edges of the greaseproof paper to make a parcel.
Transfer to the oven and bake for ten minutes, or until the fish is just cooked. Remove from the oven and set aside in a warm place.
Meanwhile, for the Thai-style salad, place the herbs, olive oil, lime juice, cherry tomatoes and soy sauce into a small bowl and stir together. Set aside.
For the lime butter sauce, heat the olive oil in a small saucepan, add the onion and fry over a gentle heat until softened but not coloured.
Add the white wine and simmer until the liquid has reduced by half. Add the cream, lime zest and salt and freshly ground black pepper and simmer for a further 2-3 minutes.
To serve, place the fish parcel onto a serving plate and open. Place the Thai-style salad inside the parcel beside the fish and pour over the lime butter sauce.