Heat olive oil in a large pot over medium heat.
Add the diced onion and sauté until translucent, about 5 minutes.
Stir in the minced garlic and cook for an additional minute.
Add the pumpkin puree and mix well.
Pour in the vegetable broth and stir to combine.
Add coconut milk and mix thoroughly.
Season with cinnamon, nutmeg, salt, and pepper.
Bring the mixture to a gentle simmer and cook for 15 minutes.
Blend the soup until smooth using an immersion blender.
Serve hot, garnished with fresh sage leaves.