01 - Season the beef cubes evenly with salt and freshly ground black pepper.
02 - Heat a large skillet over medium-high heat and sear the beef cubes in batches until browned on all sides; transfer browned beef to the slow cooker.
03 - Add carrots, parsnips, potatoes, onion, celery, and minced garlic into the slow cooker with the beef.
04 - In a mixing bowl, whisk together beef broth, dry red wine (if using), tomato paste, dried thyme, dried rosemary, and bay leaves; pour this mixture over the beef and vegetables.
05 - Cover and cook on low setting for 8 hours or on high for 4 to 5 hours, until beef is fork-tender and vegetables are completely cooked.
06 - If a thicker consistency is desired, stir the cornstarch slurry into the stew 30 minutes before serving and continue cooking on high until thickened.
07 - Remove bay leaves, taste the stew, and adjust seasoning as necessary.
08 - Sprinkle freshly chopped parsley over the stew before serving.