Miso Noodle Soup

Bland Alert: My children (ages 5 and 3) love this soup and have been eating it for years. My husband is less of a fan, probably because it is not that exciting.
At the time you begin to prepare the soup, bring a separate medium sized pot of salted water to boiling and cook about 8 ounces udon or soba noodles. When the noodles are done, drain and rinse with cold water until the soup is ready.
In a 4 to 5 quart soup pot, heat the oil and saute the carrots and sweet potatoes if using. I usually let them cook and soften for about five minutes. Sprinkle on the nutritional yeast and add the ginger. Let it cook for another minute or so, then add the water and kombu. Bring to a boil over high heat, then turn the heat to medium and simmer for a good ten minutes, until the carrots are soft.
Add the broccoli (if using) and a few minutes later add the peas. You might need to raise the heat after adding the vegetables to return the soup to a simmer. After the vegetables simmer for a couple of minutes, add the tofu and let the soup return to a simmer for another minute or two.
Put the miso in a cup and stir in a couple of spoonfuls of soup broth to the miso until it is liquidy and not lumpy. Turn off the heat and mix the miso into the soup to taste (I usually use a lot). Add the tamari and a couple of drops of sesame oil (it quickly overpowers everything so I usually just put in a couple of drops).
To serve, first put the noodles in a shallow bowl, then put a couple of pieces of shredded spinach on top. Ladle the soup over the noodles. Pick out the kombu and ginger and discard.