After the 30 minutes, you will notice the solids settled to the bottom and the liquid is on top.
If you want to replace the water on top, gently pour the liquid into a measuring cup. Take note of how much liquid is poured out. Discard this liquid. Then add "fresh" water back into the batter.
If you don't want to replace the water on top, just give the batter a whisk to make sure the liquid and solids are well combined.
Place a pan equipped with a lid on the stove and turn the heat to low. Allow the pan time to heat up.
Using a ladle, pour the batter on the pan and spread the batter out by moving the pan around until it covers the entire pan. Make sure the batter is spread out thinly.
Cover the pan and let the batter steam for 3 minutes.
Place a spoon full of the filling in the pan.
Using a spatula, gently fold the batter over the filling.
Transfer the filled steamed rice rolls on a plate & give the pan a quick wipe with a paper towel. I find wiping the pan helps me roll the next steamed rice roll.