Heat the olive oil and butter in a saucepan on medium-high heat. Add the onion and sauté until soft. Add the rice and sauté until all the rice is coated. Add the vermouth or white wine, and stir until all the liquid is absorbed. Keep adding the hot broth, 1/2 cup at a time, until it is all absorbed in the rice and the rice is tender; add more liquid, if needed.
Stir in Parmesan cheese and fresh parsley, and serve warm.
Makes 4 servings