In a large pot, heat the olive oil over medium heat. Add the chopped onion and sauté until it becomes translucent, about 5 minutes.
Stir in the minced garlic and grated ginger, cooking for an additional 1-2 minutes until fragrant.
Add the diced sweet potatoes and ground cumin to the pot, stirring well to combine.
Pour in the vegetable broth, ensuring that the sweet potatoes are submerged. Bring the mixture to a boil, then reduce heat to a simmer. Cook for about 20 minutes, or until the sweet potatoes are tender.
Once cooked, remove the pot from heat. Using an immersion blender, puree the soup until smooth. Alternatively, you can transfer the soup in batches to a countertop blender.
Return the smooth soup to a low heat, and stir in the can of coconut milk. Mix until fully combined and heated through. Season with salt and pepper to taste.
Serve the soup hot, garnished with fresh cilantro and a squeeze of lime juice for added brightness.
Notes
For a spicier version, add red pepper flakes or cayenne pepper.