Remove the skin and the pin bones from the mackerel fillets and then cut the fish into small cubes. Finely chop the capers and gherkins. Pick and chop the parsley leaves. Finely dice the red chilli. Combine all the ingredients in a bowl and leave to refrigerate.
Using a vegetable peeler, peel the cucumber into long strips. Leave to marinate in the vinegar, sugar, salt and fennel seeds.
Place a ring mould in the middle of your plate. Spoon the mackerel tartare into the ring and press down. Top with creme fraiche and sprinkle with poppy seeds. Remove the ring and then finish the dish with the cucumber ribbons.
«Always make sure your fish is as fresh as possible when making tartare as you are eating it raw.»