Place the stew meat, salt, pepper, Worcestershire sauce, beef broth and ketchup. Pour over the meat. Cook for 7-9 hours on low or 4-5 hours on high.

About 30 minutes before serving, combine the flour and apple juice in a small bowl, whisking vigorously to combine well. The roux should be thick but still pourable so add a tablespoon of apple juice or water at a time to thin, if needed. Pour the flour mixture into the slow cooker, whisking quickly to mix in the roux with the stew meat and juices and to avoid lumps. Add the mushrooms and stir. Cook on high for 30 minutes.

Stir in ½ cup sour cream right before serving. Serve over pasta, rice or baked potatoes.