Bring a large pot of lightly salted water to a boil. Add pasta and cook for 8 to 10 minutes or until al dente; drain.
In a frypan over medium heat, cook bacon and onion in the butter for 7 to 8 minutes. Add mushrooms and cook 2 to 3 minutes more. Stir in the heavy cream, salt, pepper, blue cheese and tomato sauce; cook for 5 minutes, stirring continuously. Pour over cooked farfalle pasta and serve.