1. Spray a 5 qt. slow cooker with cooking spray.
2. Add beef, mushrooms and garlic to slow cooker.
3. In a medium bowl, mix broth, wine, flour, rosemary, salt and pepper with wire whisk until blended.
4. Pour over beef mixture.
5. Cover; cook on low 10 hours or until beef is tender.
6. Heat potatoes according to package directions; stir in sour cream.
7. Serve beef over potatoes.