In a saucepan, add the pickling liquid ingredients and bring to the boil.
Julienne the daikon and place into a bowl. Pour the pickling liquid over the daikon (through a sieve) and leave to pickle for ten minutes.
n a large bowl, place the avocado flesh, wasabi, lime juice and a large pinch of salt. Using a whisk, whip the mixture until smooth. Set aside.
Roll the tuna in the sesame seeds until the fish is evenly coated and place into a hot pan with a little grape seed oil and sear for 15 seconds on each side. Remove from the heat and slice thinly.
To make the dressing, combine the soy, mirin and vinegar. Shred the pickled ginger with a sharp knife.
To assemble the dish – add a spoonful of the whipped avocado to the plate, 4-5 slices of the tuna, top with pickled daikon and garnish with ginger and shiso leaves. Pour a little of the dressing over the tuna to finish.