Place a pot of water to boil. Meanwhile in a skillet sauté onion with olive oil until translucent, about 3-4 minutes.
Add butternut squash and sauté three minutes, stir in broth and bring to simmer, cook thoroughly, about ten minutes.
Cool the sauce down and process ½ it in the blender until smooth, combine with the diced butternut squash.
Meanwhile in a small skillet heat up butter until it turns light brown, add sage and Brussel sprouts and sauté until caramelized and thoroughly cooked, season with salt and pepper. Set aside.
Cook pasta according to directions, drain and toss with butternut squash sauce. Serve topped with Brussel sprouts and [optional] Parmigiano.