Heat olive oil in a large pot over medium heat.
Add chopped onion and sauté for 5 minutes until translucent.
Stir in minced garlic and grated ginger; cook for another minute.
Add diced sweet potatoes and ground cumin; mix well.
Pour in vegetable broth and bring to a boil.
Reduce heat and simmer for 20 minutes, or until sweet potatoes are tender.
Use an immersion blender to puree the soup until smooth.
Stir in coconut milk and season with salt and pepper.
Heat through for an additional 5 minutes.
Serve hot, garnished with fresh cilantro.