1. Bring a large pot of salted water to a boil and cook pasta until al dente according to package directions, reserving half a cup of pasta water before draining.

2. Heat olive oil or butter in a large skillet over medium heat, add cubed chicken, season with salt and pepper, and sauté until golden and cooked through, then remove chicken and set aside.

3. In the same skillet, add a bit more oil if needed and sauté chopped onion until translucent, then stir in minced garlic and cook until fragrant.

4. Reduce heat, add pumpkin puree and stir to combine with the onion and garlic mixture.

5. Gradually pour in heavy cream, whisking until smooth, then warm over low heat until the sauce begins to thicken.

6. Stir in fresh or dried sage or thyme, add red pepper flakes, and season with salt and pepper to taste, then simmer gently to meld flavors.

7. Return the cooked chicken to the skillet and add drained pasta, tossing with tongs to coat evenly in the pumpkin sauce.

8. Add reserved pasta water as needed to adjust consistency, sprinkle with Parmesan if desired, and serve immediately.