This lovely salad is perfect with oily fish like mackerel and salmon, as well as poached chicken and roast leg of lamb. Boil 500 g baby waxy potatoes in lightly salted water until cooked. Meanwhile, slice 1 red onion into thin rings and toss with 4 tablespoons white vinegar (cider or rice vinegar works well) and leave to ‘cure’. Drain the potatoes once cooked, then slice them in half lengthways while still hot (use a pair of tongs for this) and put in a bowl. Drain the vinegar from the onions and pour it over the hot potatoes, season generously with freshly ground pepper and salt, add 4 tablespoons extra-virgin olive oil and mix together. Leave to cool, then mix in the onion rings and a small handful of snipped dill.