01 - In a large skillet over medium-high heat, sear the beef cubes on all sides until browned. Transfer to the crockpot.
02 - Add carrots, parsnips, butternut squash, potatoes, onion, celery, garlic, and mushrooms to the crockpot.
03 - In a bowl, whisk together beef broth, red wine (if using), tomato paste, and Worcestershire sauce. Pour over the meat and vegetables.
04 - Add salt, black pepper, thyme, rosemary, and bay leaves. Stir gently to combine.
05 - Cover and cook on low for 8 hours, or on high for 4-5 hours, until the beef and vegetables are tender.
06 - About 20 minutes before serving, mix cornstarch with cold water to make a slurry. Stir into the stew, cover, and cook on high for 15-20 minutes, until thickened.
07 - Remove bay leaves. Taste and adjust seasoning if needed. Garnish with fresh parsley before serving.