To prepare the sauce: Heat butter in a pan. Add onions and saute. Add sliced mushrooms and cook. Add the bell peppers, and toss on high heat. Add the cream, herbs, salt and pepper powder to taste. Boil the pasta in salted water with oil, till done. Drain and keep aside. Bring the mixture to a boil and remove from heat. Mix pasta well into the hot sauce. Add seasoning. Serve hot.