Oven baked sea trout fillets simply seasoned with dill and lemon are in fact oven steamed: the delicate tasty fish cooks in steam, in an ordinary oven, at low temperature.
Never overcook fish!
Overcooked fish is one of the cardinal cooking sins in my books. I can take not-quite-pink lamb. I can stomach overdone beef if it is of good provenance, and unless charcoaled.
Duck is an accommodating bird: crispy Peking shredded into pancakes is as nice a thing as duck magret à point. But if you let fish cross the line between nicely flaking and stringy dry, that’s a catastrophe. Fishastrophe, even.
Salmonidae (pink fish to you and me) are particularly frequent victims of fishastrophe. Look away while grilling and your tasty, fatty salmon fillet turns into compressed sawdust. Poaching isn’t always the solution: I’ve had (or attempted to have) poached fish tasteless and dry as anything.
Easier said than done
It is really tricky to hit the moment of doneness-yet-succulence. Personally, I can eat my salmon raw but most people will balk at translucent fish flesh. True, those people will probably not mind the desiccation but cooking is about more than just 'not minding'. We should all strive at perfection!
Prodding fish with temperature probes is not always reliable considering the thinness of an average fillet. And prodding it with a knife and fork to see if it flakes easily ruins the presentation. The culinary aesthete in me disapproves.
How to perfectly bake sea trout
This method makes things easy and it works much better than wrapping fish in foil parcels. You still need to mind the time but the combination of low temperature and steam gets you at least halfway there.
If you’re a lucky owner of an oven with moisture injection function, you needn’t faff around with hot pans and boiling water. Simply set the oven to the relevant programme at the temperature indicated in the recipe below.
The rest of us mortals need to create steam, not unlike what happens when baking bread. To achieve that, you need to set up a steam source in the oven, on a rack below the one the fish will be baking.
The most effective way to generate lots of steam is to actually boil water in a cast iron dish or a heavy frying pan and transfer it, hot and full of boiling water, into the oven. But I am reluctant to advocate such a risky enterprise: better place the vessel in the oven whilst it heats up and just when the fish is about to go in, pour in boiling water from the kettle. That's a much safer approach.
When is sea trout in season?
Sea trout is a seasonal fish, available in the UK in summer. It's the salty water cousin of brown trout, bigger and hence less boney which is always a plus. It is usually sold whole, filleted by my kindly fishmonger, so I always need to freeze some of it in portions. And considering defrosted fish is even more prone to drying out, I religiously cook it with steam as described below.
The seasoning needs to be simple but if you do get hold of smoked salt, you won't regret seasoning your fish that way. Apart from salt and pepper, just a little olive oil and lemon will suffice, and lots and lots of fresh dill which is really wonderful with pink fish.
And samphire - another seasonal sign of summer, and so delicious with fish. If you're not partial to sea vegetables (though samphire is marvelously rich in nutrients and lean in calories), serve the sea trout with some land green veg: broccoli or green beans.