In a small saucepan, over medium heat, heat the chicken broth. Leave it on low heat while you cook the risotto. If you think you'll need more broth, add it to the pan to warm up as you cook the risotto.
Heat the olive oil in a 3 - 5 ½ quart dutch oven or large saucepan over medium-high heat. Stir in the onions and cook, occasionally stirring, until translucent and fragrant, about 4 minutes.
Stir in the leeks, and cook for about 5-6 minutes or until fragrant and pieces of onion are golden.
Stir in the arborio rice until it's coated with oil, and cook for about 1-2 minutes until the edges are translucent.
Reduce to medium heat and pour in the wine and let it boil until the rice absorbs it.
Ladle ½ cup or more chicken broth into the pot, barely covering the rice. Continue to cook, occasionally stirring, until the rice has absorbed the broth and you can see the bottom of the pan.
Continue this process, adjusting the heat as you need to. The rice and broth should cook gently, and you don't want it to boil because the bottom will burn. As you stir more broth into the risotto, the rice mixture will become thick and creamy but still al dente. You want to taste it as it cooks to tell when the risotto is done cooking. This process takes about 20 minutes but can be less or more, depending on the consistency you want. If you want a thicker consistency, use less broth or more for a creamier texture. Keep in mind that the risotto should be al dente, so it's done cooking when it's creamy but still has chew. It will continue to cook as it sits, but you don't want to add more broth because the risotto can get mushy.
Once the risotto cooks, remove it from the heat and stir in the butter and parmesan cheese. Give it a taste for salt and pepper. Start with about ¼ teaspoon of salt, give it a taste and add a little more if needed.
Serve with more grated parmesan cheese and fresh parsley.