In a saucepan, bring broth to a simmer on low heat.
In a large pot or dutch oven, heat olive oil over medium heat. Add onion and saute for 3 minutes or until the onion begins to soften. Add the rice and continue to saute for 1 minute.
Add 1 cup of broth and cook while stirring for a couple of minutes until the water is absorbed. Add a 1/2 cup of broth and stir until it is absorbed. Continue this process of adding 1/2 cup of broth at a time until the rice is cooked and creamy. This will take about 20 minutes. If your broth is running low, add more or add water to the simmering saucepan to ensure there is enough warm liquid to use.
Once the rice is cooked, turn off the heat. Add the butter and Parmesan and stir to incorporate. Taste the risotto and add salt and pepper as needed. Sprinkle with parsley and Parmesan before serving, if desired.