4 fish each weighing at least 8 oz / 250 g
salt and pepper
juice of 1 lemon
3 tbsp butter
soup vegetables, coarsely diced (2 carrots, 2 celery stalks, 1 leek, a bunch of parsley)
1 onion spiked with a bayleaf
4 allspice berries
2 tbsp flour
1 cup cream 250 ml
3 tbsp hot mixed mustard
2 egg yolks
a dash of wine vinegar
Wash the fish, pat dry, and season with salt and pepper. Sprinkle them with the lemon juice, and let them stand for 15 minutes.
Meanwhile, melt 1 tbsp of the butter, and gently fry the soup vegetables in it. Add 6 cups/1 1/2 liters of water, the onion, and the allspice berries, and simmer for 10 minutes. Then add the fish steaks and cook gently over low heat for about 8 minutes. Lift the fish out and keep it warm; strain the liquid.
Melt the remaining butter and add the flour, stirring. Blend with 1 cup/250ml of the fish stock, stir in the cream, and simmer together for a few minutes. Mix the mustard, egg yolks, and wine vinegar together. Take the sauce off the stove, stir in the egg yolk mixture, and season to taste with salt, pepper, and sugar. Serve with boiled potatoes or buttered vegetables.