For the mango salsa: Slice the dashi kombu and shiso leaves as thinly as possible. Dice the mango into small cubes. Toss the dashi kombu, shiso leaves and mango together on a cutting board and chop as finely as possible to combine. Set aside.
For the halibut crudo: Sprinkle the halibut with sea salt, wrap in the dashi kombu and refrigerate for 30 minutes to marinate.
Slice the halibut into 5 thin pieces the size of sushi nigiri (about 2 inches long and less than 1/2 inch thick). Place 5 dots of ponzu sauce (about 1 teaspoon each) on a plate. Roll the halibut slices and stand them on their side on the dots of ponzu. Add 2 drops of the white truffle oil and about 1/2 teaspoon mango salsa to each piece of halibut. Then add a small dollop (1/2 teaspoon or less) of the wasabi tobiko and an even smaller dollop of the black caviar to each piece of halibut. Serve.
This recipe was provided by a chef, restaurant or culinary professional. It has not been tested for home use.
Recipe courtesy of executive chef Ritsuo Tsuchida, Blowfish Sushi, San Francisco, CA