Preheat oven to 400°F (200°C). Place acorn squash halves, cut-side down, on a baking sheet lined with parchment paper. Bake for 45-60 minutes, or until tender when pierced with a fork.

Let the squash cool slightly, then scoop out the cooked flesh and set aside. Discard the skins.

Heat olive oil in a large pot or Dutch oven over medium heat. Add the chopped onion and cook until softened, about 5 minutes.

Add the minced garlic and cook for another minute until fragrant.

Add the cooked squash flesh to the pot along with the vegetable broth, sage, and nutmeg. Bring to a simmer, then reduce heat and cook for 15 minutes, stirring occasionally, until the flavors have melded.

Carefully transfer the soup to a blender (or use an immersion blender) and blend until smooth and creamy. Be cautious when blending hot liquids.

Return the soup to the pot. Stir in the heavy cream or coconut milk (if using). Season with salt and pepper to taste. Heat through gently.

Ladle the soup into bowls and garnish with toasted pepitas or croutons, if desired.