1.Stand daikon in bowl of iced water for 15 minutes; drain well.
2.Place tuna on chopping board; using very sharp knife, cut 6mm slices at right angles to the grain of the fish, holding the piece of skinned fish with your fingers and slicing with the knife almost vertical to the board.
3.Divide tuna slices among plates; mound equal amounts of daikon next to tuna.
4.Garnish plates with equal amounts of wasabi and pickled ginger; serve with separate bowl of soy sauce.
Raw fish sold as sashimi has to meet stringent guidelines regarding its handling and treatment after leaving the water. We suggest you seek local advice from authorities before eating any raw seafood. Daikon, also known as giant white radish, is used in Japanese cooking; it has a sweet, fresh flavour without the bite of the common red radish. Use a mandoline (if you own one) to shred the daikon. You’ll need a piece of daikon about 7cm long and 5cm in diameter for this recipe.