Use the coarse side of a box grater to shred the tofu.
Add the grated tofu to a mixing bowl along with sriracha, vegan kewpie mayo, salt, and kombu dashi powder (if using). Mix until fully combined and creamy.
Remove the pit and peel the skin from your avocado.
Place the avocado flat side down and cut into 1cm wedges. Set aside.
Use a spoon to gently scrape out the watery seeds from the center of your cucumber half.
Cut the deseeded cucumber into 8 evenly sized sticks. Set aside.
Get ready to roll:
Place your bamboo sushi mat smooth side up and lay a half sheet of nori rough side up on top.
With wet hands, grab about 120–130g of rice (roughly the size of a medium apple) and spread it evenly across the nori, right to the edges and corners.
Sprinkle roughly 1 tablespoon of vegan caviart across the rice in a thin, even layer.
Carefully flip the entire sheet so the rice and caviar are now facing down and the nori is on top.
Spoon a strip of your tofu mixture lengthways across the center of the nori, about 1 inch wide and ½ inch thick.
Lay two cucumber sticks alongside the tofu mixture, then place avocado wedges gently on top.
Grab the bottom edge of the mat and roll it over the fillings, using your fingers to keep everything in place and tuck the roll tightly.
Hold the mat in place with one hand while pulling the top part away with your other hand to create tension and seal the roll.
Roll once more so the seam rests on the underside. Gently press along the sides to shape and seal.
Plate up!
Place your roll on a chopping board and slice into bite-sized rounds (2–3 cm thick). Use a sharp knife, clean the blade with a damp cloth between cuts, and rinse under cold water as needed.
Plate your sushi with optional wasabi, soy sauce, or pickled ginger.