Soak the dried porcini mushrooms in 2 cups of warm chicken broth for 20 minutes, then strain and reserve the liquid.
Heat olive oil and 1 tablespoon of butter in a large pan over medium heat. Add the onion and garlic and sauté until translucent.
Add the Arborio rice to the pan and stir continuously for about 2 minutes until the rice is well-coated and slightly toasted.
Pour in the white wine and cook, stirring, until the liquid has mostly evaporated.
Begin adding the warm chicken broth gradually, including the reserved mushroom soaking liquid, one ladle at a time, stirring often. Wait until the liquid is mostly absorbed before adding more.
Continue this process for about 20 minutes, or until the rice is creamy and tender but still has a slight bite.
Stir in the remaining 2 tablespoons of butter and the grated Parmesan. Season with salt and pepper to taste.
Serve immediately garnished with additional Parmesan if desired.
Notes
For a richer flavor, use homemade chicken broth and freshly grated Parmesan cheese. Serve with a crisp white wine.