In a large saucepan, bring the chicken broth and one cup water to a boil over medium-high heat, then turn the heat to low.
In a large skillet, heat the EVOO, about two turns of the pan, over medium-high heat. When the EVOO is rippling, add the onion and garlic and cook, stirring occasionally, until softened, about two minutes. Add the rice and toast for three minutes. Stir in the wine and cook, stirring occasionally, until mostly evaporated, 2-3 minutes.
Add two ladlefuls of the warm chicken broth to the rice and stir until the liquid evaporates. Repeat with the remaining broth, cooking the risotto until creamy, about 18 minutes. During the last three minutes of cooking, stir in the squash; season with nutmeg, salt and pepper. During the last minute of cooking, stir in the cheese and butter. Top with the sage.