Preheat your oven to 400°F (200°C). Spread the cubed pumpkin on a baking sheet, drizzle with a tablespoon of olive oil, and roast until tender and slightly caramelized, about 25-30 minutes.
While the pumpkin roasts, heat a tablespoon of olive oil in a large pot over medium heat. Add the chopped onion and sauté until translucent and fragrant, about 5 minutes.
Add the minced garlic, ground nutmeg, and chopped sage to the pot. Cook for another minute until the mixture is aromatic, filling the kitchen with a warm scent.
Add the roasted pumpkin to the pot, stirring to combine with the aromatics. Pour in the vegetable broth, bringing the mixture to a gentle boil.
Lower the heat and let the soup simmer uncovered for about 10-15 minutes to meld the flavors and allow the pumpkin to break down further.
Use an immersion blender to blend the soup directly in the pot until smooth and velvety. Alternatively, transfer carefully to a blender and puree until silky, then return to the pot.
Stir in the heavy cream, if using, to add richness and create a luscious texture. Season with salt and pepper to taste.
Once well combined and heated through, ladle the soup into bowls, garnishing with roasted pumpkin seeds for crunch and added flavor.
Enjoy the soup while hot, appreciating its creamy texture and warm, seasonal spices that evoke autumn's cozy atmosphere.
