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 to 10 minutes. While chestnuts are still warm, quickly peel off the outer brown shell and remove the papery thin skin underneath

Heat oil in large saucepan over medium heat. Add leek and cook, stirring often, for 3-4 minutes until tender. Add mushrooms and cook, stirring often, for 3 minutes until softening. Stir in chestnuts and stock, cover and bring to the boil

Reduce heat and gently simmer, uncovered, for 30-35 minutes or until chestnuts are soft. Remove from heat

Using a hand blender, blend soup until smooth. Simmer over low heat until hot. Season to taste. Ladle into serving bowls. Drizzle with cream or top with a dollop of yoghurt and serve. Top with pan-fried sliced chestnuts for a crunchy garnish, if desired