Cook the rice noodles in a large pot of boiling water until soft and tender (will take much less time than regular pasta) and do NOT salt the water! Drain, rinse and set aside.
In a large soup pot add about 1/4 cup broth and saute the onions and garlic until the onions start to turn golden brown.
Add the mushrooms and a generous pinch of red pepper flakes. Cook the mushroom, stirring frequently for 15-20 minutes. Do not worry if your pot is dry because the mushrooms, as they brown, will release their water and help to keep the pan moist so they don’t over cook. Also, once the water is released from the mushrooms and they become golden brown, the flavor becomes much more concentrated and is key to this amazing broth.
Add 3/4 cup tamari, 1/4 cup vinegar and 8 cups of veggie broth. Bring to a gentle simmer and simmer for about 15-20 minutes. If you taste it and think the vinegar is too strong, add a touch more Tamari. The cilantro will counteract the taste of the vinegar as well.
Add the noodles to the hot broth, the two cups of cilantro, and add a pinch more red pepper flakes. We like it spicy here so adjust according to your taste.