1) Cut 110g of the tuna against the grain into 12 thin slices. Finely chop the rest for the tartare.
2) To prepare the tartare base, combine all the ingredients and mix well. Add the chopped fish and stir lightly to combine.
3) To prepare the crispy wontons, in a saucepan, pour in the oil to a depth of 2 1/2cm and heat to 190C/Gas 5. Add the wonton skins and fry, turning once, for 8-10 seconds on each side, until light golden brown. Keep the wontons flat by using tongs to uncurl them. Using a wire skimmer, transfer to paper towels to drain. Allow to cool.
4) In a bowl, combine all of the ingredients for the dressing and mix well.
5) To assemble, first roll the tuna slices up into rose-shaped bundles. Reserving 2 tablespoons of the radish sprouts, stack in the following order: wonton skin, one sixth of the tartare mixture, shiso leaf, wonton skin, one sixth of the smoked salmon, radish sprouts, wonton skin, two tuna rolls.
6) Sprinkle the top of the each napoleon with the reserved radish sprouts. Drizzle 3 tablespoons of the dressing around each plate. Garnish with pickled ginger and tobiko.
To serve, cut through the entire stack with a knife, and smash the layers together with a fork to blend the flavours.