1Heat oil in 12-inch skillet over medium-high heat. Cook beef in oil about 5 minutes or until brown on all sides. Sprinkle with caraway seed and salt.
2Place beef in 5- to 6-quart slow cooker. Place onions, sauerkraut and 1/4 cup of the beer around beef.
3Cover and cook on Low heat setting 6 to 8 hours.
4Remove beef from cooker; cover to keep warm. Mix flour, remaining 1/4 cup beer and the mustard in small bowl; gradually stir into juices in cooker. Increase heat setting to High. Cover and cook 15 to 30 minutes or until slightly thickened. Serve beef with juices.