Fish Bon Femme

For two people
200g of white fish
60g of mushrooms
Shallots - teaspoon
Parsley - teaspoon
White wine - four tablespoons (60ml?)
Cream 80ml
Butter 10g - to spread on paper
Butter 45g non salt
One egg yolk
Potato
Salt, pepper

Remove the mushroom stalk, slice in 2mm slips, butter the dish and put a layer of mushrooms, shallots and parsley, put the fish on and then the remainder of the mushrooms over. Cover with salt and pepper, pour on the wine, put on the heat and once boiling cover with buttered paper. Heat on a low heat for 10mins. Meanwhile cut the 45g of butter in four ; also 90% beat 2 tablespoons of cream. Pour the juice into the saucepan and leave the fish in a warm place. Heat on a strong fire, add the rest of the cream and beat with a whisk, then put on middle flame and add the beaten butter. Add the yolk and beat quickly, add half the beaten raw cream and then add more to thicken it if required. Serve up with the fish.