Gently heat the chicken stock in a saucepan. Add the saffron threads, cover the pan and leave to infuse. Clean the ceps, remove the stalks and dice roughly.
Melt 20 g (¾ oz) butter in a nonstick saucepan and add the chopped onion. Cook until it turns golden then add the ceps. Sauté briefly then add the chopped parsley. Set aside and keep warm.
Melt the remaining butter in a heavy-based saucepan. Add the rice. Dampen with the wine and let the grains absorb the liquid. Remove the saffron from the stock.
Add a small ladleful of chicken stock to the pan, allow the rice to absorb the liquid, then add another ladleful of stock. Continue adding the remaining hot stock little by little, each time waiting until the last spoonful has been fully absorbed.
Remove the pan of rice from the heat and add the grated Parmesan. Let stand for a moment before mixing in. The rice will take on a creamy consistency. Add the diced ceps and blend in well. Serve immediately.