Cook rice in a rice cooker with the water and pinch of salt. Add the sugar, rice vinegar and potato starch.
Line a sheet with plastic wrap and press the rice really well, like extremely well. You want it like ⅓-½ inch thick depending on preference. Cover with the plastic wrap, place another container over it with some cans for weight. Refrigerate for 8-12 hrs and then place in the freezer for 30 min.
Add everything for the eel sauce to a saucepan. Simmer for 5-7 min or until it coats the back of a spoon. Let cool.
Cut your rice squares. This yields between 14-16 depending on the size you cut them. Fry on medium heat for about 5-7 min per side or until very lightly golden. Let rest on a sheet pan at room temp for up to 3 hrs.
Chop your tuna really finely, almost like a paste. Add the lemon zest, japanese mayo, sriracha, chives, sesame oil, tamari and sugar. Mix.
Give your rice the final fry on medium high heat until fully golden. About 3-4 min per side MAX.
Pipe your tuna on the rice, top with eel sauce, avocado and jalapeno.
