Break up ground meat into a large skillet, and add onion, mushrooms, garlic powder, and mustard powder. Cook and stir over medium heat until the meat is browned and onion is tender. Drain off excess fat.
In a small bowl, combine sour cream, mayonnaise, and beef broth. Stir into beef mixture, and cook over low heat for 10 to 15 minutes. Do not stir too much.
Meanwhile, cook pasta in a large pot of boiling water until done. Drain. Serve sauce over hot noodles.