Preheat oven to 400°F/200°C.

To a large baking sheet spread the pumpkin, onion, carrot and parsnip. Drizzle with 1/4 cup (60 ml) olive oil, 1 teaspoon salt, 1/2 teaspoon pepper and mix well. Spread in a single layer and roast for 30 minutes until the vegetables are tender. Remove from the oven and set aside.

Add 1 tablespoon olive oil to a large soup pan over medium heat. Add the celery and leeks and cook for 5 minutes until softened then add the corn and garlic and cook for 1 minute. 

Stir in the cumin, coriander, curry powder and nutmeg to the pan and stir well to combine. Cook for 2 minutes until fragrant to cook the spices. Add the stock, roasted vegetables, bay leaf and stir. Bring to a simmer. Cover partially with a lid and simmer for 10 minutes.

Turn off the heat, remove the bay leaf and leave to cool slightly for 10 minutes.

Blend the soup in a blender or use an immersion blender until smooth. Return to the pan stir in the sour cream and heat over low heat. Taste for seasoning, add more salt or pepper if needed.

Serve warm.