Put the onion, rosemary, and hot pepper in a heavy-bottomed 4-quart pot, drizzle with 2 tablespoons extra virgin olive oil, and stir to coat the onion with the oil. Cook over low heat until the onion is soft.
Add the rice, stir to coat with the oil, and cook for a few minutes to lightly toast.
Add the squash and stir to combine with the rice. Add the wine if you are using it and raise the heat to evaporate the wine.
Add the simmering vegetable broth (or boiling water and a little salt) 1 cup at a time, stirring frequently with a long wooden spoon or fork, over highest heat. Boiling risotto attains the temperature of molten lava and it's wise to keep one's distance while stirring. Add more vegetable broth when risotto is still surrounded by liquid, stirring often. After about 10 minutes of cooking begin to add broth 1/2 cup at a time. Taste the rice after about 15 minutes of cooking. It should be firm under tooth, al dente, since it will still cook for a few minutes. Liquid should be a little soupy because the Parmigiano cheese, oil (or butter), and final whipping will tighten up sauce, which should be opaque, bathing individual kernels.
Add the grated cheese and the remaining extra virgin olive oil (or 2 tablespoons butter) and stir energetically with a long-handled wooden spoon or fork, over high heat to whip the ingredients together.
Remove from heat, ladle into individual bowls, and let risotto rest for a minute before serving. Top with additional Parmigiano if desired.
Recipe courtesy of Gourmet Magazine