1. Place chicken stock in a saucepan and bring to a boil, reduce heat to low and keep at a gentle simmer.
2. Heat oil and 40g butter in a heavy based pan over medium heat, add pancetta, onion and garlic, and cook for 8 minutes or until onion is soft.
3. Add rice and cook for 2 minutes until well coated in onion mixture. Add wine and simmer until almost evaporated. Add stock to pan, a ladleful at a time, stirring continuously, allowing the stock to be absorbed before adding the next. When you have about 250ml (1 cup) of stock left, stir in the parmesan and season with sea salt and freshly ground black pepper.
4. Remove pan from heat, stir in remaining stock, cover pan and set aside while you cook the mushrooms.
5. Heat remaining butter in a large frying pan over high heat until foaming. Add mushrooms, thyme and chestnuts and cook, turning, until mushrooms are golden. Add cavolo nero and cook until wilted.
6. To serve, spoon risotto among shallow bowls, top with the mushroom mixture and scatter with a little extra parmesan.
* Cavolo nero, literally, 'black cabbage', is available from specialist greengrocers. The dark green, long crinkly leaves are usually sold in bunches.
Recipe by Sophia Young published in Vogue Entertaining & Travel June/July 2008