Prepare the batter: in a large bowl, hydrate the starches by whisking together the rice flour and tapioca starch with the room temp water (see ingredients list for amount). Once hydrated, whisk in the neutral oil (or shallot oil if using). Complete the batter by adding the boiling water and salt, mix well and rest for as long as you can, overnight is best.
Prepare the filling: in a frying pan, heat up a bit of oil over medium high heat. Add the shallots and cook, stirring, until soft and translucent, about 1-2 minutes.
Brown the ground pork, breaking into pieces as it cooks. When the pork is cooked, stir in the wood ear mushrooms.
Add the oyster sauce, fish sauce, sugar, and white pepper. Stir and cook for 1-2 minutes, then remove from the heat and let cool.
Prep your station: have a large cutting board for the rolling surface, neutral oil or shallot oil in a cup with a brush, a serving plate to put your finished rolls on, and the prepared filling. Lightly brush a layer of oil onto the cutting board and serving plate.
Make your rolls: Heat up a bit of oil in a non-stick 8 inch frying pan or square tamagoyaki frying pan over medium-low heat. Stir the batter well with your ladle and then pour a thin layer of batter (about 2 tbsp) onto the pan. Cover and cook for 2-4 minutes. When you lift the cover off, the rice paper should be translucent and puffing up from the bottom of the pan.
Finish your rolls: Tip the rice sheet onto the prepared cutting board and spoon in some of the filling. Carefully roll up the rice noodle sheet up and over the filling. Place the completed banh cuon on the prepared serving plate, and lightly brush with oil.
Repeat until all the banh cuon are made. Top the prepared fish sauce and toppings or side as desired.