Heat olive oil in a large pot over medium heat. Add the chopped onion and garlic, sautéing until softened, about 5 minutes.

Add the cubed pumpkin to the pot and cook for another 5 minutes.

Pour in the vegetable broth and bring the mixture to a boil. Reduce heat and simmer for 15-20 minutes, or until the pumpkin is tender.

Use an immersion blender to puree the soup until smooth, or transfer to a blender in batches.

Stir in the coconut milk or heavy cream, cinnamon, nutmeg, salt, and black pepper. Simmer for 5 more minutes, then adjust seasoning to taste.

Serve the soup hot, garnished with roasted pumpkin seeds if desired.