Heat the oil in a large pan. Add the onion and garlic and cook for 8-10 minutes, until softened. Add the risotto rice and wine, and simmer until reduced by half.
Begin adding the stock, a ladleful at a time, waiting until it has absorbed before adding the next ladle. Continue, stirring regularly, until all the stock has been used and the rice is cooked through (20-25 minutes).
About 5 minutes before the end of the cooking time, add the broccoli, beans and chicken.
Stir through the watercress and parmesan, season to taste with salt and freshly ground black pepper, then serve.