2 pounds yellowfin tuna fillets -- chopped fine by

-- hand, removing any -- sinew 3 tablespoons finely chopped scallion

2 tablespoons freshly grated gingerroot

2 teaspoons dijon-style mustard

1 tablespoon soy sauce

cayenne -- to taste salt and freshly ground pepper vegetable oil spicy wasabi mayonnaise: 1/2 cup bottled mayonnaise

1 tablespoon wasabi powder mixed with water to make a

-- paste 1 tablespoon fresh lime juice

pickled cucumber ginger relish: 1 seedless cucumber -- peeled, cut in

-- half and very -- thinly sliced 1 small red onion -- very thinly sliced

2 tablespoons finely chopped pickled ginger -- available in

asian -- specialty stores and gourmet food shops or 2 -- tablespoons grated fresh gingerroot 1/4 cup seasoned rice vinegar -- available in most

-- major supermarkets -- or 1/4 1 cup white wine vinegar plus 1 tablespoon

-- sugar 4 brioche rolls or other soft roll

In a bowl combine the tuna, scallions, gingerroot, mustard, soy sauce, cayenne, salt and pepper. Form the mixture into six 1-inch patties and chill for 30 minutes.

In a small bowl whisk together the mayonnaise, wasabi, and lime juice. Cover and chill.

In a medium bowl combine the cucumber, red onion, pickled ginger, and rice vinegar. Toss to coat and season with salt and pepper.

Heat a dry large heavy skillet over moderately high heat. Brush each tuna pattie with the vegetable oil. Cook the tuna patties for 5 to 6 minutes per side until they are just cooked through. Transfer the tuna patties to the buns and top with the wasabi mayonnaise and the pickled cucumber ginger relish.