Heat up the broth, in the meantime chop the onion in small pieces and put it in a pan, with the oil.
When the onion is golden and soft, add the rice and mix it until it becomes golden too.
Now add the wine and make sure to cook it on high heat for a few minutes.
When the alcohol will evaporate, add a ladelful of broth to the pan, and begin to mix it.. When almost all the water will be gone, add more broth. You will have to repeat this procedure until the rice is ready.
After 10 minutes, taste the rice to understand if you need to add some salt. After more or less 15/20 minutes, the rice will be cooked. Cooking time depends on the type of rice, but it should be soft with a slight bite in the center.
Once the rice is ready, turn off the heat. There should still be some broth in the pan, but not so much as to cover the rice.
Add the saffron, the butter and the parmesan cheese to the pan and mix it for a couple of minutes, and look at the magic happen. Now you can serve your risotto with a dash of pepper and some more cheese on top, if you feel like it.