Heat the olive oil in a large pot over medium heat until shimmering. Add the chopped onion and sauté for about 5 minutes, until it becomes tender and translucent with a gentle aroma filling the air.
Add the minced garlic and cook for another minute, stirring constantly until fragrant and slightly golden.
Stir in the pumpkin puree, blending it into the aromatic onion and garlic mixture. Let it cook for 2 minutes to meld the flavors.
Pour in the vegetable stock, stirring well to combine. Bring the mixture to a gentle simmer and cook uncovered for 15 minutes, allowing the flavors to develop and the soup to thicken slightly.
Add ground cinnamon and chopped sage to the soup, stirring to evenly distribute the spices. Continue simmering for another 5 minutes.
Use an immersion blender to carefully blend the soup directly in the pot until smooth and velvety, or transfer in batches to a regular blender, then return to the pot.
Stir in the heavy cream for added richness, then taste and season with salt and black pepper as desired.
Return the soup to a gentle simmer for a few more minutes to heat through. Serve hot, garnished with a swirl of cream and additional sage if desired.
