In a large skillet, over medium-high heat, saute ground beef, garlic, onion, mushrooms, mustard powder, salt and pepper until meat is browned and onion and mushrooms are tender. Drain off excess fat and liquid.
Meanwhile, in a small bowl, combine sour cream, mayonnaise. Stir into beef mixture and let simmer about 10 minutes.
Plate noodles and top with stroganoff or mix noodles in and serve.