Prepare noodles according to package directions; drain.
Meanwhile, slice round steak into 1/4-inch thick strips. Heat a large skillet over medium-high heat, spray with vegetable cooking spray and brown steak. Add water, mushrooms and onion soup mix. Bring to a boil, cover, reduce heat and simmer for 15 minutes.
In a small bowl, combine yogurt and flour. Add to the meat mixture. Cook until thickened; stirring frequently. Serve hot over cooked noodles.Servings: 4