Futomaki Sushi: They add a delicious umami flavour and a soft texture that pairs well with the other ingredients in these Vegan Futomaki Rolls. Shiitake Mushroom Roll: Consists of seasoned sushi rice, nori (seaweed), and sliced simmered shiitake mushrooms as the filling. Nigiri Sushi: To make this, you will need whole simmered shiitake mushroom caps, add this on top of a small mound of sushi rice and secure with a strip of nori.