Instructions

  1. Pat roast dry with paper towel.
  2. In a skillet, heat oil over medium-high heat.
  3. Add roast and cook, turning, until brown on all sides, about 7 to 10 minutes.
  4. Transfer to slow cooker.
  5. Reduce heat to medium.
  6. Add onions, celery and carrots to pan and cook, stirring, until vegetables are softened.
  7. Add garlic, mustard, thyme, salt and pepper and cook, stirring, for 1 minute.
  8. Sprinkle mixture with flour and stir.
  9. Add tomato soup and beef broth and cook, stirring, until thickened.
  10. Stir in Worcestershire sauce.
  11. Pour mixture over roast, cover and cook on LOW for 10 to 12 hours or on HIGH for 5 to 6 hours, until meat is very tender.
  12. Remove roast from slow cooker and place on serving platter.
  13. Stir in brown sugar and vinegar, if using, to pan juices.
  14. Pour sauce over roast or serve in a separate sauce boat.