Rinse and soak noodles in hot water to soften, if necessary depending on the kind of noodles you chose. Shiratake simply need to be rinsed, but some cellophane and udon may need to be soaked in hot water to soften before adding. Drain when done.
Wash and chop all veggies and tofu.
In a large soup pot or dutch oven, sauté the green onions and mushrooms with a little veggie broth (or neutral tasting oil) until slightly browned. Remove and set aside to add later.
Add water, Tamari (or other), mirin, sake and sugar to the pot and simmer until the sugar is dissolved. Add broccoli and carrots to the pot. Simmer for a few minutes. Then add bok choy and cabbage.
Simmer a few more minutes. Then turn heat to low and add mushrooms, green onions, tofu and noodles. Allow to warm for a few more minutes until everything is just cooked. Turn off heat and serve.
You can arrange the veggies and tofu into group around the outside of the pot, then add the noodles in the center for presentation, but it isn’t necessary.