Peel and cube the sweet potatoes. The smaller you cut them the faster they will cook.
Dice the onion.
Finely chop the celery.
Peel and dice the carrot. Then mince the garlic.
In a large, heavy bottomed pot, heat the oil over medium heat.
Add the onion, celery, carrot, and garlic.
Cook for 5 minutes, stirring regularly, until the onion starts to get translucent.
Add the sweet potato, ground ginger, and broth plus a cup of water.
Cover and cook over medium-low heat for 30-40 minutes until all the vegetables are extremely soft.
Add the miso paste, salt, and pepper.
Remove from the heat and use an immersion blender or stick blender to pulse everything until smooth. Alternatively, allow to cool slightly and then use a regular blender.
Taste and adjust the salt to preference.
Optional: Garnish with fresh parsley.