01 - Heat olive oil and 1 tablespoon butter in a large, heavy-bottomed saucepan over medium heat. Add chopped onion and cook until softened and translucent, about 3 minutes.
02 - Stir in minced garlic and diced squash. Cook, stirring occasionally, until squash begins to soften, about 5 minutes.
03 - Add Arborio rice and cook, stirring constantly, for 2 minutes until grains are well coated and slightly translucent at the edges.
04 - Pour in white wine and cook, stirring, until mostly absorbed by the rice.
05 - Begin adding warm vegetable broth one ladleful at a time, stirring frequently. Wait until most liquid is absorbed before adding more. Continue until rice is creamy and al dente and squash is very tender, about 20 to 25 minutes. You may not need all the broth.
06 - Stir in chopped sage, remaining butter, Parmesan cheese, and heavy cream if using. Season with salt and pepper to taste.
07 - Remove from heat, cover, and let rest for 2 minutes. Serve hot, garnished with extra Parmesan and sage leaves.