Preheat your oven to 400°F (200°C), then spread the pumpkin chunks on a baking sheet, drizzle with olive oil, and toss to coat. Roast for about 30-35 minutes until they are golden brown and easily pierced with a fork.
While the pumpkin roasts, heat a tablespoon of olive oil in a large pot over medium heat. Add the chopped onion and cook for 5-7 minutes until translucent and fragrant, with a slight golden color.
Add the minced garlic to the onions and cook for another minute, until it becomes aromatic and slightly softened.
Once the pumpkin is roasted and cools slightly, add the soft, caramelized chunks to the pot with the sautéed aromatics. Pour in the vegetable broth to help blend everything smoothly.
Use an immersion blender or transfer the mixture in batches to a blender, then blend until smooth and velvety. This step creates the creamy, uniform base of the soup.
Return the blended soup to the pot and stir in the heavy cream to enhance richness. Warm the mixture gently until steaming, but avoid boiling.
Season the soup with salt and pepper to taste, adjusting the seasoning as needed for balance and flavor.
Ladle the hot soup into bowls, garnish with fresh sage leaves if desired, and serve immediately with crusty bread or your favorite sides.
