Bring the stock to the boil and keep at a low simmer.
In a large saucepan heat the olive oil and add the onion. Sweat the onions over low heat for 3 to 5 minutes; don't allow them to take any colour.
Add the rice and mix well. Pour in the white wine and cook over medium heat until most of it evaporates; about 3 minutes.
Add a ladle of hot stock to the rice stirring well. After about 3 minutes when most of the stock has been absorbed; add another ladle of stock. Repeat in this fashion until the rice is tender and cooked through; about 20 minutes.
Add the Parmesan and mix well. Taste the risotto and add salt and pepper if desired. Serve immediately.