crub 300g of small, waxy potatoes and bring to the boil in deep, salted water. Simmer for 15 minutes or so, until tender to the point of a knife. Remove the skin from a whole smoked mackerel and ease the flesh from the bones. Make a dressing by putting 2 tbsp each of red wine vinegar and olive oil in a mixing bowl, then stir in 1 tsp of smooth Dijon mustard, 100ml of crème fraîche and 100ml of natural yogurt. Season with salt and pepper, 8 sliced cornichons and 2 tsp of drained capers. Finely chop 4 spring onions and 4 sprigs of dill, then add them to the dressing with some picked parsley leaves. Drain the potatoes and add to the dressing, tossing them gently so they are evenly covered. Peel, seed and roughly chop 1 small cucumber. Wash 2 large handfuls of crisp, cos-type lettuce leaves, cut them into manageable pieces then add to the dressing, with the cucumber and mackerel. Toss everything together and divide between 2 bowls. Enough for 2 The trick Handle the smoked mackerel gently, so the pieces stay fat and juicy and aren’t crushed when tossed with the potatoes. If you can find it, use whole smoked mackerel rather than fillets. The whole fish has softer, more creamy flesh. The twist Use other smoked fish in place of the mackerel, such as smoked trout. Air-dried meats are good here, too, especially thinly sliced salami. Pastrami is one of my favourite additions to a potato salad. The Observer aims to publish recipes for fish rated as sustainable by the Marine Conservation Society’s Good Fish Guide