Preheat the oven to 220°C.
Prepare the turbot by gutting, scaling, removing fins, rinsing, and patting dry.
Melt 60g of butter and cook celery, carrots, and leeks for 4 minutes with 30ml of wine.
Stuff the fish cavity with the vegetables and spread remaining 30g of butter over the skin.
Roast the fish in the oven for 30 minutes until the flesh is white.
Boil onions, vinegar, 30ml of wine, and fish stock until reduced to two spoonfuls.
Add 240g of butter, sorrel, and spinach to the pan to soften for one minute.
Blend egg yolks while slowly pouring in the hot sauce mixture.
Strain the sauce through a sieve into a warm boat and serve with the filleted fish.