In a large saucepan add the butter and olive oil then heat over a gentle moderate heat. Add the chicken, when white all over add the onion and celery then cook until becoming transparent.
In a small saucepan add the chicken stock and thyme then bring to a simmer.
To the chicken add the rice and stir, when it has absorbed the butter and oil then add the wine. When the wine is absorbed add the chicken stock a ladle at a time, stirring after each ladle until absorbed.
When the rice is soft and the chicken stock gone stir some of the Parmesan through the risotto, and save the rest to sprinkle on top as a garnish.