Bring a large pot of salted water to a boil. Cook pasta according to package instructions until al dente. Reserve ½ cup pasta water before draining.

While pasta cooks, heat olive oil in a large pan over medium heat. Add butternut squash cubes and cook for 10–12 minutes, stirring occasionally, until soft and golden at the edges. Add garlic for the last 1–2 minutes.

Transfer cooked squash and garlic to a blender. Add cream, Parmesan, and stock. Blend until smooth and silky. Season with salt and pepper to taste.

Return the sauce to the pan. Add cooked pasta and toss to coat, adding a splash of reserved pasta water if needed to loosen the sauce.

Divide between plates, top with extra Parmesan, and garnish with fried sage leaves if desired. Serve immediately.