In a large pot, heat the olive oil over medium heat. Add the chopped onion and sauté until translucent, about 5-7 minutes.
Stir in the minced garlic and chopped sage, cooking for an additional 1-2 minutes until fragrant.
Add the cubed butternut squash to the pot and stir well. Cook for about 5 minutes, allowing the squash to slightly caramelize.
Pour in the vegetable broth and bring to a simmer. Cover and cook for 20-25 minutes, until the squash is tender.
Once cooked, use an immersion blender to puree the soup until smooth. If you do not have an immersion blender, transfer the soup in batches to a countertop blender.
Return the smooth soup to the pot and stir in the coconut milk (or heavy cream) and nutmeg. Season with salt and pepper to taste. Heat gently on low for an additional 5 minutes.
Serve the soup hot, garnished with toasted pumpkin seeds and a drizzle of olive oil, if desired.
Notes
For a richer flavor, use heavy cream instead of coconut milk.