The recipe Trim 250g of kohlrabi, cut it into thin slices, then into matchstick strips and place in a mixing bowl. Slice 20 pickled cornichons in half and add them to the bowl with 3 tbsp of their pickling liquor. Cut 200g of cucumber into thin slices, then into matchsticks and toss with the kohlrabi and cornichons, creating a crisp and piquant salad on which to place your mackerel. Season 4 small mackerel fillets (or 2 large ones). Warm 3 tbsp of olive oil in a frying pan and place the fish skin-side down in the hot oil. Sprinkle each with a pinch of paprika. Let them fry for 7 minutes or so over a moderate heat, covered by a lid, occasionally spooning the oil over them as they cook. Divide the kohlrabi salad between 2 plates, then place the mackerel on top. Spoon some of the juice from the salad over the fish and serve. Enough for 2 The trick I usually cook mackerel over a very hot grill, letting the skin crisp and brown, but sometimes it makes a change to do what we’ve done here, cooking the fish without browning, so it stays moist, juicy and surprisingly delicate in flavour. Baste it with the paprika oil, constantly spooning the spiced juices over the fish as it cooks. The twist Any fillet of fish is good for this treatment, though the oily fish are complemented by the piquancy of the pickling liquor. If you can’t find crisp, unblemished kohlrabi (the only sort worth buying), then use the thick stalks of broccoli or cauliflower, along with their florets. The Observer aims to publish recipes for sustainable fish. For ratings in your region, check: UK; Australia; US Follow Nigel on Twitter @NigelSlater