Bring the soy and mirin dressing to the boil and submerge the mushrooms into the liquid. Allow to cool completely. During this process the mushrooms will be marinated. In the meantime bring equal parts of
vinegar and sugar syrup to the boil and allow the mixture to cool completely. Trim the tuna into a long log about the size of a 50 cent piece. Rub the tuna with some oil and sear on all sides for approximately a minute or two. The outer edge should be just seared, leaving the whole centre raw. Wrap the tuna tightly in glad wrap making sure you tighten each end so that it helps to form a log like shape. Chill in the fridge to allow the shape to form.
Remove the plastic wrap and cut the tuna into five or six thin discs. Lay these on the plate, arranging them in an uneven pattern. Using a vegetable peeler, remove the skin from the cucumber. Then peel the cucumber into long thin ribbons. Plunge these into the pickling syrup and marinate for a few minutes. Strain the mushrooms from the soy and mirin dressing. Spread some of the mushrooms around the plate and place some on top of the tuna. Strain the cucumber and place a pile onto the plate. Spoon some of the dressing on top of the tuna and on to the plate. Drip some olive oil onto the plate. Garnish with some chervil leaves and serve.
Pickle for the Cucumber:
Combine equal parts of sugar and white vinegar and bring the mixture to the boil. Remove from the heat and allow the mixture to cool.
Soy Mirin Dressing
Combine soy sauce, mirin and ginger and bring just to the boil. Remove from the heat and add the lemon
juice. Allow to cool and refrigerate in air tight container.