Preheat the oven to 200C/390F/Gas 6.
Dry the scaled, gutted fish with kitchen paper. Stuff the body cavity with the thyme.
Whisk the egg whites in a bowl until soft peaks form when the whisk is removed. Fold the salt into the egg whites.
Line a baking sheet or ovenproof serving dish with greaseproof paper and spread one-third of the egg white mixture over the base.
Lay the sea bass on top of the egg white mixture, and then spoon over the remaining mix to cover the fish completely.
Bake the sea bass in the oven for 30-35 minutes, until the salt crust is crisp.
Remove the dish from the oven. Break the salt crust with a palette knife. Using a pastry brush, remove the salt crystals from the surface of the fish and from around the fish.
Squeeze over the lemon juice and drizzle with olive oil.
For the fennel salad, place the fennel, dill, orange juice and olive oil into a bowl and mix together.
Leave to stand for about ten minutes. Just before serving, add the rocket and mix to coat the rocket leaves.
For the garlic mash, place the garlic and cream into a saucepan and bring to the boil, then reduce the heat and simmer until the cream is reduced by half.
Remove the garlic bulb from the pan, then mix in the mashed potatoes and stir well to combine.
Add the butter and season to taste with salt and freshly ground black pepper.
To serve, place a spoonful of mash onto each serving plate along with a little of the salad and a quarter of the sea bass for each person.