Cheung Fun, Steamed Rice Noodle Rolls (肠粉)

Name: Cheung Fun, Steamed Rice Noodle Rolls (肠粉)
Prep time: 10 min
Cook time: 25 min
Total time: 35 min
Cuisine: Chinese
Ingredients: ½ tbsp neutral cooking oil; ½ onion, sliced; 4 cloves garlic, sliced; 2 pieces dried shiitake mushrooms, rehydrated and sliced; 120 ml water (about ½ cup); 4 tbsp light soy sauce; 1 tsp dark soy sauce; 1 tbsp oyster sauce; 2 tbsp sugar; 100 g rice flour (about 3½ oz); 50 g wheat starch, or cornstarch/tapioca starch (about 1¾ oz); ¼ tsp salt; 1 tsp neutral cooking oil (plus a little for brushing); 350 g water, room temperature (1½ cup); Scallions (finely chopped); Dried shrimp (rehydrated); Char Siu pork (sliced); Shrimp (shelled)