Step 1: In a medium saucepan, heat the chicken broth over medium heat until it reaches a simmer. Once simmering, lower the heat to maintain warmth.

Step 2: In a large pot or Dutch oven, add the olive oil and warm it over medium heat. Introduce the chopped onion, cooking while stirring frequently until it begins to soften, approximately five minutes. Incorporate the cubed butternut squash, one tablespoon of butter, and minced garlic. Cook this mixture until the squash starts to show color around the edges and becomes tender, about six minutes. Season with salt and pepper to taste.

Step 3: Add the remaining tablespoon of butter along with the arborio rice to the pot, stirring vigorously. Cook for about two minutes until the rice is well-coated and emits a slightly toasty aroma. Pour in the white wine and allow it to cook until it is mostly absorbed.

Step 4: Using a ladle, add approximately one cup of the warm broth to the rice mixture. Stir frequently, allowing the rice to absorb most of the liquid. Continue this process by adding the remaining broth, one cup at a time, ensuring each addition is absorbed before adding more.

Step 5: Stir the mixture consistently as it cooks until the butternut squash is tender, and the risotto achieves a creamy yet al dente texture, which should take around 25 minutes. Finally, mix in the grated Parmesan and chopped sage, seasoning with additional salt and pepper if desired, before serving.