01 - Heat olive oil and 1 tablespoon butter in a large, heavy saucepan over medium heat. Add the onion and cook until translucent, about 3 minutes.
02 - Stir in the garlic and diced squash. Sauté for 5–6 minutes, until the squash begins to soften.
03 - Add the Arborio rice. Stir for 1–2 minutes until the grains are well-coated and lightly toasted.
04 - Pour in the white wine and cook, stirring, until mostly absorbed.
05 - Add 1 cup of warm broth, stirring frequently. When the broth is mostly absorbed, add another cup. Continue adding broth, one cup at a time, stirring often, until the rice is creamy and al dente and the squash is tender (about 20–25 minutes).
06 - Stir in the remaining butter, Parmesan cheese, chopped sage, salt, and pepper. Adjust seasoning to taste.
07 - Remove from heat. Let rest, covered, for 2 minutes before serving. Garnish with extra sage and Parmesan, if desired.