- For the sushi rice, Combine the prepared sushi rice with the rice vinegar. Set it aside.
- For the mushroom mixture, heat the oil in a large rondeau over high heat. Add the onions and sauté until translucent, 2 to 3 minutes.
- Add the mushrooms and sauté until they start to soften. About 3-4 minutes more adding water as needed to prevent sticking.
- Add the garlic and scallion and cook until the scallions are wilted, and the garlic is cooked, 3 to 4 minutes.
- Add the sushi sauce and maple syrup and reduce until slightly thickened, about 5 minutes. Remove the mixture from the pan and set aside to cool.
- To assemble the temaki rolls, lay the nori sheets smooth side down on a clean surface. Place a scoop of seasoned rice on the left side of the nori. Wet your hand with water and spread the rice slightly outward toward the corner.
- Place some of the mushroom mixture, avocado, carrot, and cucumber, diagonally on the rice. Fold the bottom left corner upwards, like a flag, over the mixture, so that it connects to the top center of the nori.
- Take the right side of the nori and fold it over the middle of the roll, wetting the edge of the nori with some water, to seal the temaki.
- Garnish with a sprinkle of sesame seeds.