In a large skillet over medium heat heat 1 tablespoon oil and add onion shallots, and garlic cook for 1-2 minutes, until shallot just starts to become translucent. Add in pumpkin or squash and cook until just about tender, about 8 minutes. Add in chicken, and a big pinch of salt and pepper and continue cook until no pink remains, about 8 minutes. Add in 2 cups of spinach and cook for 3-5 minutes, until spinach starts to wilt. Remove from heat and set aside.
In a small bowl mix all sauce ingredients together and set aside. Grease a 8" x 8" (or similar sized) casserole dish and set aside.
Take spaghetti squash out of oven, let cool. Using a fork scrape out the spaghetti squash into a greased casserole pan. Add in pumpkin and chicken mixture, and top with the sauce. Top with Parmesan, if desired.
Bake at 400 degrees for 10 minutes, and broil for 5 minutes.