De-skin and de-bone the cod, setting them aside.
Blend the fish meat in a mixer and then pass it through a fine sieve.
Slowly add the unbeaten egg whites and then 100 g of the cream and the ricotta.
Adjust the salt and white pepper, stir and place in the refrigerator for 20 minutes.
Heat the oven to 200°C.
Sauté the Shad sacks in butter, take off their skins and sprinkle with salt and black pepper.
Open one of the egg sacks, mince it into tiny pieces and mix it into the egg mousse.
Butter a ring-shaped mould and pour in the mixture.
Put the mould in pot with boiling water, cover with wax paper and cook it in the oven for 20 minutes.
When done, release the mousse from the mould onto a hot tray and fill the centre with the following sauce, which must be ready as soon as the mousse is: In a saucepan, place the fish bones and skin together with water and the wine, add the chopped onion, carrots and celery along with the parsley, salt and pepper to taste.
In a separate bowl, beat the yolks together with the flour and 100 g of cream and then filter and pour 350 ml of the filtered fish. broth onto the flour and cream.
Put the entire composition in to a double boiler with boiling water, then add the remaining 100 g.
cream to the remaining egg sack, finely chopped.
Add salt and pepper to taste and let the sauce thicken, stirring constantly.
Remove from flame, add the lemon juice and pour this sauce into the hollow ring of the mousse mould.