Start the rice the day before or first thing in the morning - it needs minimum 4 hours to chill.
Make the toppings first, then refrigerate while you cook the crispy rice cakes.
Cook the crispy rice cakes and sprinkle with salt per the recipe.
Assemble - Place rice cakes on a serving platter. Pile on toppings - I use teaspoons to make football shapes then slide on. Sprinkle with black sesame seeds, top with jalapeño. Eat!
Freeze to firm - Place tuna in the freezer for 30 minutes to partially freeze - it's much easier to finely chop when slightly firm.
Cut into 0.5cm / ½" cubes - the smaller the better! Place into a bowl and let it de-chill for 20 minutes (not as nice ice-cold).
Mix - Add everything into the tuna and mix until combined.
Place tuna in a bowl and use a fork to mash it up really finely. Add everything else and mix well.
