In a pot over medium heat, warm the oil. Add the chopped onion, garlic, and ginger. Sauté until softened, about 5 minutes.
Add the cubed Japanese sweet potato and vegetable broth. Bring to a boil, then reduce heat and simmer for about 15 minutes, or until the potato is fork-tender.
Remove from heat. Use an immersion blender (or carefully transfer to a blender) and blend until smooth.
Return to low heat. Stir in miso paste (dissolve it in a bit of hot broth first if needed) and coconut milk Let it warm through, don’t boil once miso is added to preserve its probiotics.
Add salt and pepper, adjust as needed.
Ladle into bowls and garnish with the green onion tops and an extra swirl of coconut milk or sesame oil if you like.
