Heat the coconut oil in a large pot over medium heat. Add the onion and sauté until soft and translucent, about 5 minutes.
Stir in the garlic and ginger and cook for 1 minute, until fragrant.
Add the sweet potatoes, carrots and turmeric, stirring to coat.
Pour in the vegetable stock, bring to a boil, then reduce the heat and simmer for about 20 minutes, until the vegetables are very tender.
Blend the soup until smooth using an immersion blender (or carefully in batches in a countertop blender).
Stir in the coconut milk, season with salt and pepper, and warm through.
Serve hot, garnished with fresh cilantro.