Preheat oven to 200°C (180°C fan-forced)

Cut a shallow cross into the flat side of each chestnut shell. Place prepared chestnuts onto a baking tray and bake for 15 to 20 minutes or until the shells split open

Once cooked, remove chestnuts from the heat and wrap in a clean tea towel for 5 minutes. While chestnuts are still warm, quickly peel off the outer brown shell and remove the papery thin skin underneath

Heat 2 tsp oil in a large saucepan over medium-high heat. Add pancetta and cook, stirring often, for 3 minutes or until crispy. Transfer to a plate. Set aside

Heat the remaining 1 tbsp oil in the pan over medium heat. Add onion, celery, garlic and chillies and cook, stirring often, for 4-5 minutes until softened

Add chestnuts and pumpkin and cook, stirring occasionally, for 5 minutes. Stir in stock and three-quarters of the pancetta. Cover and bring to the boil. Reduce heat, cover and simmer, stirring occasionally, for 20-25 minutes or until pumpkin and chestnuts are tender

Puree soup with a stick blender until smooth. Season to taste. Cover and bring to the boil over medium heat. Ladle soup into serving bowls. Top each with a dollop of sour cream, the remaining pancetta and extra sliced red chilli and serve