Cook pasta as pkg. directs. In large skillet, heat olive oil. Add onions and cook on medium heat for 4 minutes. Add sausage, mushrooms, and garlic and cook 4 minutes. Add chile flakes, tomato paste and broth. Bring mixture to a boil, then reduce heat to simmer and cook for about 20 minutes.
Remove 1/2 cup of cooking water from pasta and add to the sauce. Drain pasta and add to sauce. Stir in parsley and continue cooking til liquid is almost evaporated. Top with cheese and serve. Makes 4 servings.