- Using a large cup or bowl, combine the rice flour, tapioca starch with the room temperature water and boiling water. Whisk for a few minutes combining well. Let the batter rest for 30 mins.
- Soak the dried wood ear mushrooms in a bowl of warm water for 10 mins. Drain well and then finely chop.
- Finely dice the yellow onion.
- Season the ground pork with salt and pepper and then mix well.
- Heat a wok over medium low heat. When hot add the ground pork and wood ear mushrooms. Cook for 5-6 mins, stirring it constantly. Use a spatula to break the meat into small pieces. Add the diced onions and cook for another 2 mins. Transfer the filling into a clean bowl.
- Take the batter that’s been resting and carefully pour out just the clear liquid from the top into a measuring cup. Make note of the amount poured out then discard this liquid. Measure out the same amount of fresh water and pour into the batter. Add the salt and vegetable oil into the batter. Mix well.
- Brush vegetable oil onto the work surface.
- Heat an 8in non-stick skillet over Low heat until hot and then lightly oil. Pour 1/8 cup batter into the hot skillet. Swirl the skillet to coat it evenly with the batter. Cover with a lid and cook for 45-60 secs. Remove the lid and flip the pan over the work surface to remove the cake. Allow to cool for 1 min. Place a heaping tablespoonful of the meat filling at the top of the cake. Fold over the sides and then roll-up the cake. Continue making the cakes until you run out of ingredients.
- Dunk the bean sprouts in boiling water for 1 min. Remove and drain well. Cut the cucumbers into ⅛in slices and then into thin strips. Coarsely chop all herbs. Cut the steamed pork roll into thin slices. Arrange the vegetables and pork roll on a large plate.
- To serve, place the banh cuon rolls on a plate. Top with the bean sprouts, cucumbers, fresh herbs and steamed pork roll. Sprinkle with fried onions and serve with a generous side of fish sauce dipping sauce.