For a richer flavor, try roasting the pumpkin cubes before simmering. Toss them with a little olive oil, salt, and pepper, and roast at 400°F (200°C) until tender and slightly caramelized. If you don't have an immersion blender, you can carefully puree the soup in a regular blender. Be sure to vent the lid to prevent pressure from building up. Feel free to adjust the amount of sugar and seasoning to your liking. A pinch of cinnamon or nutmeg can also add a lovely warmth. For a vegan version, substitute vegetable broth for the chicken broth and use a plant-based yogurt alternative.