"It's still alive!" cries Adrien, appalled. The flesh is soft like gelatinous butter and the colour of blushing putty. I gingerly put a sliver in my mouth. "I can't believe you're eating it while it's still alive!" Henry, who is eight, makes a grimace; Orla, his little sister is already heaving over the side.
"It's amazing!" I say. It is. It isn't at all like the shaved fillets of sashimi or carpaccio I am used to. The texture is squashy and creamy; the taste is a delicate rendering of essential elements: sea and blood and iron.
"Mackerel is my favourite fish," Nathan Outlaw tells me when I visit him in his new restaurant in Port Isaac a few days later. Outlaw is the only British chef with a Michelin-starred fish restaurant, and it is two-starred.
"Mackerel is a fish you should eat as soon as you catch it. Sprats, herring, sardines, anchovies are all the same family and the fresher the better. I've had mackerel straight out of the sea, cured in seawater for 10 minutes. Wonderful! In the old days the fisherman would just add vinegar."
Optimum window for eating
Not all fish is best eaten super fresh. Just like meat, the proteins and enzymes that are released post-mortem have an effect on flavour and texture. Aside from the mackerel family, Outlaw tells me that for most fish, the optimum window for eating is between two and five days old.
Turbot will keep improving for up to 10 days, for example, while eating it fresh on the day it is caught "would be like eating a table", Outlaw says. Similarly, on the few occasions he had served very fresh Dover sole, customers had complained that it was tasteless. A good rule of thumb is the oilier the fish, the quicker it will go bad.
The best process, he says, is for the fisherman to gut a fish as soon as it is caught and then keep it whole on ice. This would mimic, to some extent, how animals are slaughtered: killed and then aged. But fishermen sell their catch by the weight and are unenthusiastic about doing the extra work of cleaning only to be rewarded with a lower price.
Outlaw points out that fresh fish is almost a misnomer. Day boats will catch coastal fish and crab and lobster, but trawlers after deep sea species such as cod, hake or skate will go out for up to a week at a time. The fish has been sitting on ice at the bottom of a boat for several days by the time it is landed and sold at auction. "Market fresh" is what they call it. Add another day or two for it to get to a reputable fishmonger's slab, and more than a week for it to be transported, processed and packaged to end up in a supermarket chill counter.
Outlaw sources most of his fish from fishermen's co-operatives in Cornwall: "We're lucky here in Cornwall; we have the Gulf Stream so more of a diversity of fish than in the north of England."
Every fish has its own properties and peculiarities, and seasonality is also an important factor in determining texture and flavour. Mackerel is an active fish and has a lot of blood; sea bass is a scavenger with a different diet depending on the time of year. When the herring has a high season in November, Outlaw buys in bulk, salts them for six weeks and then preserves them under oil, the same method as Mediterranean anchovies.
Back at the house we have a haul of mackerel. Some I skin and fry; some I grill until their skin bubbles and blackens. I cut ragged slices for carpaccio and dress them very simply with salt and lemon juice and olive oil. And I make a Cornish ceviche with parsley and tarragon and spring onion and plenty of lemon and lime juice to "cook" it; cayenne to finish.
"Why is it that fish tastes better by the sea?" my brother Michael asks as we all tuck in. There is none left over for smoked mackerel pâté.
Visitors to London can also enjoy Nathan Outlaw's seafood restaurant fare at The Capital Hotel, Knightsbridge. capitalhotel.co.uk
