Smoked Mackerel and Horseradish

A thumb under the corner of the skin lifts it off a hot-smoked mackerel fillet in one bronzed sheet, and the flesh beneath breaks into a few big amber flakes that go straight onto buttered bread. That is as far as the cooking goes. The smokehouse kiln cooked the fish through before it ever reached the kitchen, set firm and opaque all the way in, so the job needs neither a pan nor a blender, only flakes laid on whole in pieces you can see and feel. Horseradish goes over them, then a squeeze of lemon, and a fillet that was about the cheapest protein in the shop turns into a proper lunch for almost no work. Kept this way the fish behaves like a cold cut, sliced thick onto bread rather than whipped smooth into a tub.

Horseradish is in the sandwich because oily fish needs answering. Smoked mackerel is rich and dense and coats the tongue, and a hot grated root cuts up through the oil and clears it the way it clears the fat off roast beef, doing its work in the nose more than on the palate. The balance is the only real skill in the build. Too little horseradish and the second mouthful sits heavy and one-note, all smoke and oil with nothing lifting it; too much and the burn buries the smoke that is the reason to choose mackerel in the first place. The lemon is the other corrective, a squeeze of acid that brightens the flakes and stops the richness pooling. Peppered fillets, sold in a crust of cracked black pepper, bring their own bite and want a lighter hand on the root.

Because the fish is loose, the bread has to be built to hold it. A thick-cut bloomer or a sturdy granary gives the structure a soft slice cannot, and it gets buttered to the edges first, a seal that keeps the fish oil from soaking the crumb to a damp patch by the time the sandwich is eaten. The flakes are laid on rather than piled in a heap, spread across the slice so every bite carries fish, because a clump in the middle slides out the side at the first press. Then the crunch that all that softness needs: watercress for a peppery green, cucumber in thin rounds, sometimes sliced tomato. Closed, it wants pressing once so the lid takes; open on toast, the flakes can go on twice as generously.

Tearing the pack is the loudest the smell ever gets, a gust of oak smoke and warm fish oil with the faint sweetness the brine left behind. On the bread it settles quieter and cooler. The first bite runs dense and savoury, the smoke arriving with the oil, the flakes giving softly and breaking apart rather than melting; then the horseradish lands warm at the back of the nose and the lemon cuts in bright across the top, and the watercress or cucumber snaps once against all that give. Where a stray fleck of bronzed skin turns up it brings a chewier, smokier edge. It eats heavier than a flake of white fish ever would, which is the oil, and that weight is exactly what the heat and the acid are there to carry.

It lives wherever the fish is cheap and close, which in Britain is most places near a coast. Mackerel is the summer fish of piers and harbour walls, caught by the bucketful on hand lines and feathers when the shoals come into the shallows, so cheap that anglers use it for bait, and the smokehouses turn the glut into vacuum packs that sit in every supermarket chiller through the year. The flaked sandwich is what a home cook makes of a packet grabbed with vague good intentions, the omega-3 label and the use-by date both arguing for lunch; smokehouse cafes from Cornwall to the Scottish coast lay it on their own toast for visitors who watched the boats come in. No recipe owns it, and the amount of horseradish is a private matter argued over and never written down.

It sits inside a small British family that sorts by what is done to the fish. The whipped reading, the smoked mackerel pâté sandwich, takes the same fillet and beats it with cream cheese and lemon into a bound spread, a smoother bite from the identical packet; this one keeps the flake intact and treats it like sliced cold meat. Kipper and the old potted fish pastes are the saltier, herring-and-jar end of the same shelf. The hot mackerel fillet on bread is the plainest member of the line, a closed loaf wrapped around flakes of smoked fish, asking for nothing but a hot root and a wedge of lemon to set it right.

The smokehouse and the cheap fish

The defining fact is that the fish is hot-smoked, and Britain came to hot-smoking mackerel partly by necessity. The traditional dock smokehouses had built their trade on cold-smoking cod and haddock, but the cod shortages that came with the Cod Wars over North Atlantic fishing grounds, the last and sharpest of them running from November 1975 to June 1976, pushed curers to work other species; mackerel and trout are oily and lean toward hot-smoking, cooked through in the kiln rather than merely cured cool. The fillet that fills this sandwich is in that sense a product of fish smokers adapting their kilns when the white fish ran short, and they had a cheap glut to work with: mackerel run in colossal shoals around the British Isles through summer, taken on hand lines off rock marks, piers and harbours so readily that a fresh one costs a pound or two and anglers reach for them as bait.

The pairing with horseradish is the older idea grafted onto the newer fish. Grated horseradish has answered rich British meat and fish for centuries, the standard hot root beside roast beef, and bringing it to oily smoked mackerel applies a long-settled corrective to a fillet that only became a supermarket staple in the late twentieth century. The firm dated thread under the sandwich runs through the fish: the cod shortage that peaked in 1976 turned British smokehouses toward an oily coastal fish so abundant the harbours sold it for bait.