The Mushroom and Caramelized Onion Roll is a savory and flavorful vegetarian sushi roll. It is made by sautéing mushrooms and caramelizing onions before rolling them in sushi rice and nori seaweed. The umami-rich flavors of the mushrooms and the sweetness of the caramelized onions create a delicious combination. This roll is often served with soy sauce and a sprinkle of chopped green onions.