Preheat oven to 350º F. Spray a casserole dish with non-stick spray. Set aside.
Bring a large pot of water to boil and cook the pasta 2 minutes shy of the package directions. Drain and set aside.
In a large skillet brown Italian sausage and onion together for 5-6 minutes, breaking apart, until the sausage is cooked through and the onions are soft. Drain any excess grease. Add garlic and cook for 1-2 minutes, until you can start to smell it.
Stir in pumpkin puree and chicken broth. Bring the mixture to a boil, reduce heat and simmer for about 5 minutes until it starts to thicken slightly.
Pour in heavy cream, sage, thyme, red pepper flakes and season with salt and pepper. Once the mixture comes together add the pasta and mix until everything is evenly combined.
Pout into prepared casserole dish and sprinkle the Parmesan cheese evenly over the top. Bake for about 20 minutes until hot and bubbly and the cheese is golden brown.
Remove and serve immediately.
