Puree sea bass in a food processor, blend in egg white, and pass through a sieve.
Season with salt and pepper, then gradually stir in cream until smooth.
Wrap spoonfuls of mousse in cling film, tie securely, and chill in the fridge.
Reduce lemon juice, wine, vinegar, and shallot by half in a pan and melt butter separately.
Blend yolks, sugar, and salt, then strain in the reduction and hot butter while processing.
Stir in brown shrimps and keep the sauce warm over warm water.
Steam mousse parcels in a double boiler over gentle heat for ten minutes.
Score sea bass skin, season, oil, and grill skin-side up for four minutes until blackened.
Boil samphire with sugar for two minutes, drain, and toss with butter.
Assemble by placing fish and mousse on samphire, then glazing briefly under the grill.