Sometimes when I'm craving sushi, but I'm too lazy to prep everything, I go Tar Tar. It couldn't be simpler:
Score 2-3 cucumbers (as straight as you can find) with a channel knife, and slice crosswise into 3/4 in. sections. With a Parisienne scoop, hollow out the seedy part in the middle being careful not to scoop all the way through the bottom - we're going for cups here, after all.
If your tuna is frozen, give it a medium dice right before it thaws completely (8 oz. of tuna will yield about 15 portions). Add to this about 2 tsp of grated fresh ginger, 2 tsp of toasted sesame seeds, a dash of quality dark soy sauce, a few drops of dark sesame oil, and a splash of rice wine vinegar or a squeeze of lemon juice. Toss to coat, and let sit for a few minutes until the tuna thaws completely.
Make a bit of Sriracha Mayo by adding just enough of the Sriracha hot sauce to some mayonnaise until it's light orange in color (or spicier if you prefer). Finish with a squeeze of lime or lemon juice, and transfer to a squeeze bottle if you have one handy. Squeeze a small dab into each cucumber cup, then gently fill each cup with a heaping portion of tuna. Garnish with toasted sesame seeds. Enjoy!
