Heat olive oil in a large skillet. Add the onions and sautee for 2 minutes, until slightly softened. Add the mushrooms, rosemary, Arborio rice and garlic. Sautee for 3-4 minutes.
Add the vegetable stock and bring to a boil. Add the salt, pepper and nutmeg.
Reduce heat and begin stirring constantly for 15 to 18 minutes, until rice is cooked to al dente. Add the heavy cream and parmesan. Stir and cook for additional 1-2 minutes.
The risotto should be wavy. Not loose, and not stiff. You may add additional stock to get the proper texture.