Bring a large pot of salted water to a rolling boil. Add penne pasta and cook until al dente, about 8-10 minutes. Reserve ½ cup pasta water before draining.

In a large skillet, heat olive oil over medium heat. Add sausage, breaking it up, and brown for 5-7 minutes.

Push sausage to the sides and add minced garlic to the center. Sauté for 1 minute until fragrant.

Stir in pumpkin purée, chicken broth, and heavy cream. Add nutmeg and season with salt and pepper. Simmer for 5-7 minutes until thickened.

Add drained pasta to skillet and toss to coat with sauce. Adjust consistency with reserved pasta water if needed. Stir in Parmesan cheese.

Serve hot, garnished with additional Parmesan, parsley, and red pepper flakes.