How to make it
Slice your portabella mushroom and stir-fry in a pan until they are cooked through. Set aside to cool.
Lay out your bamboo sushi rolling mat and place a square piece of plastic wrap on top of that. Lay a large square piece of seaweed on top of the plastic wrap. (note: there is a rough side and a smooth side to the seaweed. Lay the rough side up).
Next prepare your sushi rice in a bowl by adding 2 heaping cups of cooked rice and 2 tablespoons of sushi vinegar. Put the rice on top of the seaweed layer (it should cover the most of your seaweed, but leave about a half inch on each side of the seaweed sticking out so that the roll will stick together at the end).
Place the cooked portabella mushrooms down the center in a row down the middle of the rice. Next, lay kaiware sprouts next to the mushrooms and drizzle the mayo on top of the ingredients.
Begin to roll from the side of the mat closest to you and stop half way. Squeeze tightly to get the ingredients to stick together well, then continue to roll to the end and squeeze again. To cut, wet your knife so that the blade doesn't stick to the rice. Makes 8 pieces. Serve with Otafuku Sushi Sauce.