See steps below for a steaming option if you don't have a microwave. You can also see some troubleshooting + tips below!
Prepare your tray or dish. I highly recommend having 2 dishes. This way you can finish making these rolls faster since one can be in the micrwave while one can be cooling.
Brush a thin layer of oil on the surface.
Mix the batter again to make sure the starch isn’t sitting/stuck at the bottom. It's important to mix the batter before each round.
Scoop around 1/3 cup of the batter (or depending on the size of your dishes) and place it into the oiled baking dish. Add enough mix to evenly cover the surface of your dish.
Cover with a lid then IMMEDIATELY microwave for 1.5 to 2 minutes or even longer (note: the time will depend on your microwave) until the rice mix is translucent throughout and you can lift the edges with the spatula.The reason why you have to immediately cook the mixture is because the starch spearates from the water and sets at the bottom of the dish.
While the roll is in the microwave, prepare the tray and pour in cold water.
After mircrowaving, place the container into the tray with water. Leave to cool for 2-3 minutes. Do not remove the lid.
Carefully scrape the sides with a spatula.
Place some of the the mushroom and chopped scallions. You can scatter it around the rice sheet.
From one end, carefully roll the rice sheet until you have a log.
Transfer to a plate and repeat for the rest of the batter.