50g grated Parmesan, plus extra to serve (optional)
small pack parsley, finely chopped
Heat the butter in a large pan over a gentle heat and add the onion. Cook for 10 mins until softened, then stir in the thyme leaves and mushrooms. Cook for 5 mins, sprinkle in the rice and stir to coat in the mixture.
Ladle in a quarter of the stock and continue cooking, stirring occasionally and topping up with more stock as it absorbs (you may not need all the stock).
When most of the stock has been absorbed and the rice is nearly cooked, add the chicken and stir to warm through. Season well and stir in the parmesan and parsley. Serve scattered with extra parmesan, if you like.