First, make the dashi (soup stock) with kombu and shiitake mushrooms. Put 2 .5cups of water, shiitake mushrooms, and kombu in a pot and simmer about for 3 minutes. Please stop heating before it comes to a boil. Let it sit after heating.
Mean while, wash and peel the sweet potato, carrot, and cabbage. Cut them into bite-sized pieces. Mince the ginger.
Before adding the vegetables to the pot, remove the kombu and shiitake mushrooms. Personally, I leave them in because both shiitake mushrooms and kombu are packed with beneficial nutrients.
Add the carrot, sweet potato, cabbage, and ginger to the pot. Simmer over low to medium heat until the sweet potato is tender.
Once the sweet potato is cooked, turn off the heat and dissolve 2 tablespoons of miso into the soup.