You might have heard of onigiri, a Japanese rice ball wrapped in seaweed, that can be filled with all kinds of tasty things. Onigirazu, on the other hand, is filled more generously and is shaped into a flattened square resembling a sandwich, which makes it the perfect lunch to take with you on the go. For this sandwich, we're making a filling that resembles the taste of tuna salad, but veganized.