This picture shows a typical Italian summer salad: fagiolini, patate e sgombro sotto olio – that is, green beans, potatoes and mackerel preserved in olive oil. It is a no-fuss, quick salad and most Italians would use shop-bought canned fish, but I have always found it very dry – and I did try also very expensive brands. Fortunately, to preserve mackerel (and tuna, for that matter – but tuna is an endangered species and it is best avoided) in olive oil is dead easy and delivers a far better product – flaky, tender and not at all dry. The key is to poach the fish extremely gently and for a relatively short time.
What you need is some, super-fresh mackerel – they must be really, really fresh because mackerel deteriorates very quickly, both in flavour and texture (much quicker than other fish).
The fish must be filleted and lightly salted. It is then placed skin side down in a frying pan where it should fit snugly. The fillets are then covered with oil: I use half extra-virgin olive oil and half rapeseed oil, because I find that olive oil alone is both a bit extravagant (money-wise) and too assertive in taste. I then add a few unpeeled cloves of garlic, some bay leaves, black peppercorns, a couple of sprigs of thyme – whatever I have available, bearing in mind that all these flavours should not overpower the fish. The oil is slowly warmed up. When I see tiny bubbles at the edges, I switch off the gas and I let the fish cool down, covered. When the oil is cold, the fish can be consumed, though it tastes better after a day’s rest in the fridge, where it can stay for up to a week. I have reused the oil and I am still alive and kicking.
Going back to that salad, a few notes:
The potatoes: I cook the potatoes in plenty of highly salted water, a trick I learnt from the exceptionally gifted Deborah Madison. I dress the (unpeeled) thickly sliced potatoes when still hot with good sherry vinegar and very little olive oil.
The beans: I am old-fashioned and I cook them in lots of salted boiling water, as quickly as possible. When the water is boiling, I add the beans and I cover the pot. As soon as the water is back to the boil, I remove the lid. All this with the gas on full. When they are done (never al dente, by the way – they taste grassy and horrible), I drain them. I never shock beans in cold water because I want to dress them while they are still hot – they absorb the olive oil much better this way.
Pickled red onions: a nice touch. I often have a jar of these delicious, quick pickled red onions in the fridge.
Other additions: capers, black olives, basil, quartered boiled eggs (five minutes in boiling water for a yolk that is cooked but still a little soft).
I assemble the salad and only then I add more vinaigrette.
On canned fish: canned tuna would be another obvious choice, of course. However, “tuna” is one of the foods we should really go easy with – tuna fish are on the brink of extinction and some of the fishing methods employed to catch them are highly destructive. You can buy “ethically sourced tuna” now but I have never been happy with their taste.
On mackerel: here in the UK I can buy fresh mackerel labeled as “sustainably sources”. I doubt check this.Good Fish Guide.