• 500 g fresh mackerel fillets, skinned
• about 300 ml sherry vinegar
• 2 large cloves garlic
• good handful of flat-leafed parsley leaves
• 60 ml sunflower oil
• 100 ml extra virgin olive oil
• sea salt, black pepper

Using a small, sharp knife, cut the mackerel into thin strips and lay in a shallow dish. Pour enough sherry vinegar over to just submerge the fish. Cover the dish with cling film and leave in the fridge for 2 hours or more.

Peel and roughly chop the garlic, then pound to a purée with a little salt using a pestle and mortar. Chop the parsley leaves fairly coarsely. Put the puréed garlic into a bowl with the two oils, season with crushed sea salt and plenty of pepper and mix thoroughly, then stir in the chopped parsley.

Remove the mackerel strips from the vinegar, rinse under cold water and pat dry, then lay in a shallow serving dish. Spoon the oil, garlic and parsley mixture over them, to coat thoroughly. Cover and refrigerate for 24 hours.

Remove from the fridge and uncover an hour before eating, to return to room temperature. Serve with sourdough or rye bread to mop up the juices.