1. Heat 1 tablespoon butter and the oil in medium-size heavy saucepan over medium heat. Add onion; saute until golden and softened, about 5 minutes. Stir in rice to coat, for 1 to 2 minutes.
2. Add 1/2 cup chicken broth; stir until liquid has been absorbed. Continue adding broth, 1/2 cup at a time, stirring constantly until each addition has been absorbed before adding the next 1/2 cup, and until there is only 1 cup broth remaining.
3. Add remaining broth, 1/3 cup at a time, stirring and cooking until rice is just cooked through. Cooking time should be about 30 minutes. Finished dish should be creamy.
4. Stir in Parmesan and remaining tablespoon butter.