Preheat the oven to 425°F. Line a large baking sheet with parchment paper.
Cut the pumpkin into large chunks. Scoop out and discard seeds and stringy pulp (save seeds if roasting later). Place pumpkin pieces, onion quarters, and garlic cloves on a prepared baking sheet.
Drizzle with about 3 tablespoons of olive oil and season with salt and pepper to taste. Toss to coat. Reserve the remaining oil for later.
Roast for 30 minutes, or until the pumpkin is tender when pierced with a knife. Remove the dish from the oven and let it cool for about 10 minutes.
Peel the pumpkin skin and discard it.
In a Dutch oven, heat reserved olive oil over medium heat. Add roasted pumpkin, onion, and garlic. Sauté 2–3 minutes to bring flavors together.
Pour in stock. Bring to a boil, then reduce to a simmer. Cook uncovered for 20 minutes.
Remove from heat. Carefully transfer soup to a blender in batches, covering the lid with a towel for safety. Blend until smooth and creamy. (Alternatively, use an immersion blender directly in the pot.)
Return soup to the Dutch oven. Stir in cream and gently heat through—do not boil.
Serve hot with your choice of toppings.
Notes
Store: Leftover roasted pumpkin soup keeps beautifully. Once it has cooled to room temperature, transfer it to airtight containers and refrigerate for up to four days. The flavors often deepen after a day, making it even better the next time you reheat it.
Freeze: Let the soup cool completely before portioning it into freezer-safe containers or bags, leaving a small amount of space at the top for expansion. Freeze for up to three months. When you’re ready to enjoy it again, thaw the soup overnight in the refrigerator.
Reheat: Reheat gently on the stovetop over low to medium heat, stirring occasionally until heated through. Avoid boiling once you’ve added dairy, as it can cause the soup to separate. If it thickens slightly during storage, stir in a splash of broth or milk to restore its silky smooth texture.
Make Ahead: You can easily make this roasted pumpkin soup ahead of time for busy days or gatherings. Roast the vegetables up to two days in advance and refrigerate until you’re ready to finish the soup, or prepare the entire recipe (without adding cream) and store it for up to three days. When ready to serve, reheat gently, stir in the cream, and season to taste.