01 - Preheat your oven to 325°F.
02 - Pat the beef roast dry with paper towels. Season all sides with salt and pepper.
03 - Heat vegetable oil in a large Dutch oven over medium-high heat. Sear the roast on all sides until well browned, about 3–4 minutes per side. Remove and set aside.
04 - In the same pot, add onions, carrots, celery, and garlic. Sauté for 3–4 minutes until slightly softened.
05 - Stir in tomato paste, and cook for 1 minute.
06 - Return the beef to the pot. Pour in beef broth and Guinness (if using), and add Worcestershire sauce, thyme, and bay leaves. Bring to a simmer.
07 - Cover the pot and transfer to the oven. Roast for 2 hours.
08 - Add potatoes to the pot, cover, and continue roasting for 1 more hour, until the beef is fork-tender and vegetables are cooked through.
09 - Remove bay leaves. Slice or shred the roast, sprinkle with fresh parsley, and serve hot with vegetables and pan juices.