In a large mixing bowl, add 72 grams of rice flour, 16 grams of tapioca starch, 28 grams of potato starch, 16 grams of glutinous rice flour, and ½ teaspoon of salt. Blend all dry ingredients together.
Add the two cups of filtered water in the dry ingredient bowl and whisk together. Rest the liquid for at least 20 minutes on the counter.
Char siu filling
Chop your char siu into small pieces about three millimeters.
In a saucepan, add one tablespoon oyster sauce, ½ tablespoon light soy sauce, ½ tablespoon dark soy sauce, two teaspoons sugar, 1/16 teaspoon five spice, one clove minced garlic, and one teaspoon sesame oil and mix thoroughly. Cook this on medium-high heat.
Mix ½ teaspoon cornstarch and four tablespoons water in a separate bowl and add into the saucepan. When the mixture reaches a boil, lower to medium heat and continue to cook for another two minutes or until the consistency is similar to molasses.
Add half pound char siu pieces to the pan and cook for an additional minute.
Remove the char siu filling from the heat and allow it to rest on the counter.
In a small saucepan, add ¼ tablespoon of dark soy sauce, ¼ tablespoon of light soy sauce, ¼ teaspoon of sesame oil, ½ teaspoon of sugar, one tablespoon of water, and ½ tablespoon of oyster sauce. Heat over medium-low heat and stir until the sugar is dissolved. Remove from heat and place into a container to cool until assembly.
Assemble your steamer, if you purchased a steamer set-up follow the instructions. If you’re using a tray and a saucepan follow the instructions. Place the wire rack on the saucepan and add enough water so that it sits directly underneath the wire rack. Add the tray on top (making sure it fits inside), then add the lid on top. Pre-heat this steamer before steaming any liquids.
When your steamer is nice and hot, open the lid. Brush on some vegetable oil on the tray.
Use the whisk to combine all the starches and flours that have settled to the bottom of the mixing bowl before adding the liquid onto the pan. Scoop enough liquid so that it covers the tray. If need be, move around the tray so that the liquid is evenly spread out.
Cover the tray with the lid and steam for about two minutes. After two minutes, check to see if the rice paper has firmed enough so that there is less liquid moving around. Test this by moving the tray around. If there is too much liquid and it is not sticking to the tray, place the lid back on and steam for an additional one or two minutes. Once it’s firm enough, sprinkle the char siu filling evenly across the rice noodle. Cover the steamer again and steam for an additional five minutes.
When the rice noodle is finished steaming, take a silicone spatula and carefully lift one side of the rice paper (the short edge). Fold about one inch of rice noodle over itself and continue to roll until it reaches the other end. Carefully lift the rice noodle roll and place in a serving dish.
Let the steamed noodle roll rest for about two minutes before consuming, this allows for the texture to firm. Drizzle the seasoning sauce over the roll and add some chopped scallions if you want. Serve and enjoy.