Prepare the beef: In a large stockpot, heat olive oil over medium high heat. Cut the roast into large chunks. Salt and pepper the meat liberally. Brown the beef chunks on all sides, using a tongs to turn/hold the beef. Be careful to not crowd the meat. You may need to brown in two sessions.
Remove the meat to a plate, and add tomato paste and broth/water to stock pot. Deglaze the pan by stirring up all the brown bits from the bottom of the pan. Add the beef back in, and cook on medium heat for approximately 1.5 - 2.5 hours, or until it is fork tender. Remove meat to plate, and when cooled, shred. Reserve the broth to use later.
Prepare the soup. Using the same stock pot, heat olive oil to medium high heat, and add the leeks, celery, carrots, thyme, and salt and pepper. Sauté until slightly softened (approximately 4-5 minutes). Add garlic during the last 30 seconds.
Add tomato sauce and beef broth (can use reserved broth) to pot, and stir. Add the chopped cabbage, Worcestershire sauce, bay leaves, and salt and pepper to taste, and bring mixture to a boil. Reduce heat to simmer, and add shredded beef back in pan. Cook until cabbage is wilted. Check seasonings.
Serve with some crusty bread of your choice.
