1. Cook your brown rice and allow to cool to room temperature once done. Once it has cooled down, add the rice vinegar and mix thoroughly.
2. Cut the tofu into blocks that are not too thick and are the right shape to layer on top of the sushi rice. Cut the carrot and avocado into thin pieces.
3. Now layer the tofu, carrot, avocado and spinach on top of the sushi rice. Try and keep it as stable as possible and layer everything carefully to make the folding easier. Add sliced green onion and top it off with another layer of sushi rice.
4. Place the nori in a diamond shape with the tip pointing towards you. Add roughly a 1/3 of a cup of cooked rice and shape it into a square. Make sure you align the rice to the nori to fold properly.
5. Now, fold the corners of the nori up and over the top of the layered sushi ingredients while folding in the sides until the corners close and touch each other on the top. Turn the sushi sandwich over and leave to sit for 5 minutes to set.
6. Once set, cut the sandwich from top to bottom. Garnish with sesame seeds, sriracha mayo or serve with light tahini sauce. Enjoy!