Cook the sushi rice according to its packet instructions. Fold in the rice vinegar, sesame oil and soy sauce. Let it cool until comfortable to handle.

Mix the drained tuna with the red onion, mayonnaise, sweet chili sauce, Sriracha, soy sauce, lemon juice and optional chili powder. Prepare the cucumber, avocado and toppings.

Cut 6 nori circles, using a small bowl as a guide. Press a thin layer of cooked rice onto one side of each circle. Mix the 60 ml water, cornstarch and flour into a paste. Brush the bare nori side with the paste and press it into panko.

Heat enough oil to coat the base of a frying pan over medium heat. Fry the panko-coated side down until golden, about 1–2 minutes, adjusting the heat as needed. Lift out with tongs, drain briefly, and gently bend into a taco shape while still warm. Do not handle hot shells with bare hands.

Fill the shells with a little cream cheese, cucumber, avocado and spicy tuna. Finish with green onion, spicy mayo, teriyaki sauce, fried onions and sesame seeds to taste. Serve immediately.