Cook the pasta according to package instructions until al dente.
In a large skillet, heat olive oil over medium heat and sauté the onion until translucent.
Add minced garlic and Italian sausage to the skillet, breaking it apart, and cook until browned.
Stir in the butternut squash and thyme, cooking until the squash begins to soften.
Add fresh spinach and a splash of reserved pasta water, then stir until the spinach wilts.
Combine the cooked pasta with the sauce, tossing everything together thoroughly.
Finish with grated Parmesan cheese and serve hot, garnished with extra herbs if desired.