01 - Pat the beef roast dry with paper towels. Season all sides with salt and pepper.
02 - Heat olive oil in a large skillet over medium-high heat. Sear the roast on all sides until browned, about 3–4 minutes per side.
03 - Place carrots, parsnips, turnips, onion, garlic, celery, and potatoes in the bottom of a large slow cooker.
04 - Place the seared beef roast on top of the vegetables.
05 - In a bowl, whisk together beef broth, tomato paste, Worcestershire sauce, thyme, and rosemary. Pour over the beef and vegetables. Add bay leaves.
06 - Cover and cook on low for 8 hours, or until the beef is tender and shreds easily with a fork.
07 - Remove the roast and vegetables to a serving platter.
08 - Skim excess fat from the liquid. Whisk together cornstarch and cold water, then stir into the cooking liquid. Set slow cooker to high and cook uncovered for 10–15 minutes, until thickened.
09 - Slice or shred beef, serve with vegetables, spoon sauce over the top, and garnish with fresh parsley.