Preparation / Directions:
1. Cut the beef into thin slices across the grain. PLace in a 4-quart electric slow cooker. Add the mushrooms, scallions, onion, thyme, sherry, broth, dry mustard, and garlic pepper. Mix well.
2. Cover and cook on the low heat setting about 8 hours, or until the beef is tender, stirring once, if possible. Increase the heat setting to high.
3. Mix together the sour cream and flour until thoroughly blended. Stir a little of the hot liquid from the slow cooker into the sour cream mixture; then stir the sour cream mixture into the slow cooker, mixing well. Cover and cook on high 30 to 40 minutes, or until thickened slightly.