Soak mushroom is a bowl of cold water for 3 hours, or until softened. Drain and squeeze out excess liquid. Slice and set aside.
Soak rice noodles in cold water for 2 minutes. Drain and set aside.
In a small bowl, mix together soy sauce, and cornstarch. Set aside.
Heat 2 teaspoons vegetable oil in a wok or similar on medium high heat. Add carrot and stir for a minute. Add cabbage and some salt, stirring and tossing until softened (but still al dente). Add bean sprouts and scallion and toss until well mixed and bean sprouts are just cooked. Remove to a bowl/plate and set aside.
Return wok/pot to the medium high heat with 2 teaspoons vegetable oil. (Add protein of choice if so desired and stir fry until almost done.) Add mushrooms and stir for about a minute. Add the chicken broth, rice noodles, and pinch of salt. Stir until noodles are evenly moistened. (You won’t see extra liquid though.).
Turn off the flame and stir in the vegetables. Check and add salt to taste. (Rice noodles can be difficult to toss with vegetables because they clump together. Sometimes I use two sets of chopsticks to evenly distribute.).
Cover with a lid and rest for 5 minutes. Serve with choice of condiments (vinegar, oyster sauce or sriracha or or sambal) for guests to add on their own. Store any left-overs in an airtight container in the fridge. It will last for a week. You can reheat in the microwave.