Stuffed roast salmon trout

A fairly complex recipe with many steps, but the result is fantastic!
INGREDIENTS FOR 6 PEOPLE
1 salmon trout weighing 1 kg (ask your fishmonger to prepare it and keep all the trimmings: skin, head and bones)
200 g sole (or plaice fillets)
100 g pouring cream
80 g peeled small prawns (or prawn tails)
30 g skinned pistachios
1 egg white (keep the yolk for the sauce)
Butter for brushing
Salt, pepper
SAUCE
500 g mussels
55 g butter
25 g flour
1 shallot
1 garlic clove
2 egg yolks
250 g fish stock (made with celery, carrots, onion and trout trimmings)
Half a glass white wine
100 g strained mussel liquid
50 g pouring cream
Extra virgin olive oil
Salt (only if needed)
Pepper
I make fish stock with the fish trimmings, vegetables and a litre of water, then strain it.

I scrape the mussels, remove their beards and cook them open in a frying pan with a garlic clove and a little oil.

I shell them and set aside, then strain impurities from the liquid.

I prepare the trout.
After filleting and skinning it, I remove any remaining bones with tweezers.

I process the sole fillets in an electric chopper.

I put the mixture in a bowl and add the pouring cream.

I mix well, adding the egg white.

I season with salt and pepper.

I chop the prawns with the pistachios.

I add them to the mixture.

I brush baking parchment with butter and lay a trout fillet on it.

I spread all the filling over it.

I cover with the other fillet, pressing it into place.

I brush the surface again and add salt and pepper.

I wrap in the baking parchment and secure with several turns of string.
I bake at 180°C for about 40 minutes.

I prepare the velouté sauce.

In a small pan, I melt the butter, add the flour and fish stock and bring to the boil, stirring until thickened.

I add the cream.

I add the two yolks, mix well and set aside.

I sauté the chopped shallot in the remaining butter in a frying pan, add the shelled mussels and deglaze with white wine.

I add the 100 g mussel liquid and reduce almost by half.

I add everything to the velouté.

I taste and adjust the salt and pepper.

The trout is cooked; I let it rest for 10 minutes.

I transfer it to a serving platter with the mussel velouté around it.

Now enjoy it! Attractive and sure to impress. Yes, it takes time, but if you enjoy experimenting in the kitchen, it will be very rewarding.
It comes from the December 1990 issue of La Cucina Italiana, which I treasure and return to from time to time.