Sauteed onion and carrot until onions are translucent.
Add garlic and ginger, sauteed one more minute.
Add broth and mirin, bring to a boil, cover, reduce heat and simmer for 20 minutes.
Allow to cool 10 minutes, then dissolve miso in some of the broth, then return miso mixture to the soup.
Process soup in a food mill to retain texture.
Serve warm or cold.