The heat does something to your appetite for cooked food. By Tuesday this week I had given up on anything that required the oven, and what I came back to is the plate that has saved my summers for years: hot-smoked trout, new potatoes, watercress, and a horseradish dressing sharp enough to wake you up. Twenty-five minutes start to finish, no oven required, and the only thing that needs heat is the pan of water for the potatoes — done first thing in the morning if you have any sense, then the whole plate sits in the fridge until you can face supper.
For years this was a smoked mackerel plate — and it still works that way if you can find sustainably caught fish. But the Northeast Atlantic mackerel stock is in real trouble: the Marine Conservation Society has now red-rated it (their strongest “avoid” category), and Waitrose suspended fresh, chilled and frozen mackerel from 29 April 2026 — the first UK supermarket to do so. ICES recommended a 70 per cent catch cut last autumn; the Coastal States only agreed to 48. Hot-smoked trout — almost all UK-farmed, mostly in Hampshire chalk-streams or the Scottish lochs — is the swap I’ve settled on. Marginally pricier, marginally more delicate, and it works through the dish in exactly the same way.
It is a properly British plate. Hot-smoked trout does most of the work — already cooked, around £3.50 for a 200g pack, bringing that warm, smoky depth that makes everything around it taste like more than it should. New potatoes — Jersey Royals if you can still find them, British earlies otherwise — pick up the warm dressing better than any other potato, and they are at their peak this week. Watercress is the British summer green nobody talks about enough: peppery, cleaner-tasting than rocket, and the one leaf that genuinely thrives in our wet springs.
After fifteen years of growing my own — three on a Sussex allotment — I am increasingly convinced the best summer suppers are the ones that do not ask much of you. This one asks for a pan of boiling water and the discipline not to overdress the potatoes. The horseradish is the small upgrade that lifts it from a sad lunch into a proper supper. Around £2.40 a head, sits happily in the fridge, and the leftovers — eaten cold the next day with bread and butter — are, if anything, better.
Smoked Trout, New Potato & Watercress Salad
A no-oven summer supper — twenty-five minutes, warm or cold, around £2.40 a head. The sustainable swap for what used to be a smoked mackerel plate.
Ingredients
- Small new potatoes (Jersey Royals or British earlies), halved600 g
- Hot-smoked trout fillets, skin removed~200 g
- Watercress, tough stems removed2 handfuls / ~80 g
- Spring onions, finely sliced6
- Flat-leaf parsley, roughly chopped1 small bunch
- Chives, snipped2 tbsp
- Lemon, zest & juice½
- Good olive oil3 tbsp
- Dijon mustard1 tbsp
- Creamed horseradish1 tbsp
- Sea salt & black pepperto taste
Method
- Bring a pan of well-salted water to the boil. Tip in the halved new potatoes and simmer for 12–15 minutes, until a knife slides in with only a hint of resistance.
- Drain and tip into a large mixing bowl while still hot — the heat is what soaks the dressing in later.
- While the potatoes cook, whisk the lemon zest and juice, olive oil, mustard, horseradish and a good pinch of salt in a small jar. Taste — it should be sharp and warm enough to wake you up.
- Pour half the dressing over the hot potatoes and toss gently.
- Peel any skin off the hot-smoked trout fillets and tear the flesh into big pieces straight into the bowl. Trout is more delicate than mackerel — tear rather than flake, and leave generous pieces.
- Add the spring onions, parsley, chives and watercress. Pour over the remaining dressing.
- Toss gently with your hands — do not crush the potatoes or shred the trout. Plenty of black pepper.
- Serve warm or at room temperature with thick slices of bread and butter.
Why trout, and why now
It is worth being honest about the change. For a long time smoked mackerel was the cheapest, most reliable oily fish in a British supermarket. It is also one of the fish most under pressure right now. The Northeast Atlantic stock has been declining since 2015, and the international quota set for 2026 ignored the scientific advice by a wide margin. The Marine Conservation Society’s Good Fish Guide moved it to red — the “avoid” category — earlier this year, and Waitrose became the first UK supermarket to suspend it from the chiller cabinets at the end of April.
UK-farmed hot-smoked trout is, for now, the easy answer. Most of what you see in supermarkets is from Chalk Stream (Hampshire) or Loch Duart and similar Scottish lochs. RSPCA-Assured packs are reliable; look for the blue tick or a named UK farm on the back. Aldi’s Specially Selected line and Lidl’s Deluxe line both stock it in summer; M&S, Sainsbury’s and Waitrose carry it year-round. If your supermarket only has cold-smoked, that works too — it is closer to smoked salmon in texture, slightly less oily, but the dressing carries it.
A few notes from years of making it
The horseradish matters. Plain mustard dressing is fine; horseradish lifts the whole plate. Tracklements or a supermarket creamed horseradish both work — the kick is what cuts through the oily fish. If you really cannot face it, a teaspoon of finely chopped capers is the milder substitute.
Dress the potatoes hot. Cold potatoes refuse the dressing; warm potatoes drink it up. If you are making this ahead, boil and dress the potatoes in the cool of the morning, then add the trout, herbs and watercress just before eating. The watercress in particular wilts within an hour of being dressed.
Soft-boiled eggs turn it into more. One six-minute egg per person, peeled and halved, sits on top and makes it a fuller supper without any more effort. Useful for feeding teenagers, or for stretching the same ingredients across two meals.
Leftovers, cold from the fridge. Bring back to room temperature for fifteen minutes before serving — straight from the fridge the potatoes lose their flavour. Add a fresh handful of watercress as the original will have gone limp.
What else is in season this week
Watercress and new potatoes are the obvious heroes here, but they are joined this week by the first British broad beans, the second wave of asparagus, peak radishes, and herbs growing faster than anyone can use them. If you have a few broad beans coming through, blanched and slipped from their grey skins, they are the easiest addition to this plate — five minutes in the boiling water with the potatoes, fished out with a slotted spoon, and dropped in cold water before adding to the bowl.
For more on what to do with this week’s plot, see what to sow in May and June. For everything else about cooking and living through a hot UK week, the UK Heatwave Guide 2026 covers cooling the house, watering the plot and sleeping when the rooms are warm. And if you want the other one-pan supper from this fortnight’s Dispatch — the cooler-evening version that uses the same potatoes — the leek, potato and bacon traybake sits happily alongside this.
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