Heat the nori enough to make it supple, at about 325 degrees F for 3 minutes. Place a sheet of nori on the bamboo mat with the wider part along the rolling edge of the mat. Spread 1/2 cup of the rice over the surface of the nori, leaving about 1/2-inch of nori on the furthest edge uncovered so you will be able to seal the roll. Press the rice down firmly but gently. Place a dab of wasabi - about 1/4 teaspoon - on your finger and spread a thin ribbon of wasabi from left to right along the centerline of the rice. On top of the line of wasabi, lay a length each of fish, cucumber, and scallion. Begin rolling the edge of the bamboo closest to you, using the mat to press down on the sushi roll firmly but gently as you roll. The nori should stick to itself when the roll is complete; if it doesn't, use the cornstarch slurry to moisten it. Dip a knife in vinegared water and cut the roll into 6 even slices. Repeat for each maki. Arrange the rolls cut side up on a plate and top each roll with 1/4 teaspoon tobiko.

Note: This recipe can be used in conjunction with the other recipes for the elements of the Bento Box of sushi hors d'uvre made on the episode which also included: Traditional Osaka Style Sushi, Rice Balls, and Nigiri Sushi. Also refer to the Sushi Rice recipe as needed.