Preheat your oven to 400°F (200°C).

Using a heavy, sharp knife, carefully cut the pumpkins in half. Scoop out the seeds and fibrous strands. Place the pumpkin halves face down on a baking sheet. Roast in the preheated oven for 1 to 1.5 hours, or until very tender.

Once the roasted pumpkin is cool enough to handle, use a spoon to scoop out the flesh. This should yield approximately 5 cups of cooked pumpkin.

In a large pot or Dutch oven, melt the butter (or heat olive oil) over medium heat. Add the diced shallots and sauté until they are tender, about 4 minutes.

Add the chopped garlic to the pot and cook for an additional minute, stirring frequently.

Stir in the scooped pumpkin flesh, chicken broth, fresh sage, salt, and pepper into the pot. Bring the mixture to a boil, then reduce heat, cover, and simmer for about 15 minutes to allow the flavors to meld.

Carefully transfer the soup in batches to a blender, or use an immersion blender directly in the pot, and blend until the soup is completely smooth and creamy.

(Optional) Ladle the hot soup into bowls. Garnish each serving with a dollop of light sour cream (or 0% Greek yogurt) and a sprinkle of fresh sage, if desired.