Make sushi rice. Rinse the rice well, several times, until the water is clear. Transfer to a pot, add 1 3/4 cups of water, and cook until ready.

Meanwhile, in a small saucepan, boil the rice vinegar, sugar, and salt until the sugar and salt dissolve. Chill.

Chop the tuna,  and transfer to a bowl. Add the chopped cilantro, sriracha sauce, and mayonnaise; mix well.

Transfer the prepared rice, which has cooled slightly, to a bowl (preferably a wooden bowl). Add the cooked vinegar and toasted sesame seeds. Pour the vinegar onto a wooden spoon and spread around the bowl, so that the sauce spreads all over the rice in the bowl (not just in one spot).Gently mix; cover with a damp kitchen towel.

Wet your hands well. Using a trigger ice cream scoop, scoop rice to the palm of your hand. Flatten the rice. Take a teaspoon of the spicy tuna, put it in the center, and then close to form a ball. All balls should be the same size. If you do not have a trigger ice cream scoop, use a regular spoon, but try to make all balls equal in size.

Sprinkle chopped green onion and cilantro over the rice balls. Serve with soy sauce and spicy mayonnaise.

If you would like to tempura fry the rice balls, keep reading .....

To make the tempura:

In a bowl, mix the eggs, flour, salt, pepper, and water or beer well, for a smooth batter.

In a separate bowl place the panko crumbs. Coat the stuffed rice balls in the batter then in the panko and fry. Serve hot with soy sauce and spicy mayonnaise.

You can fill the rice balls with salmon, avocado, cheese, vegetables, and more!