Cover and cook on low for 7-8 hours or 4-5 hours on high or until meat is tender.
Remove thyme sprigs (if using). Taste, and season with salt and pepper if needed. Sprinkle with fresh parsley.
To thicken: Whisk 2 tbsp corn starch with the remaining 1/2 cup of COLD (or room temperature) beef broth. Pour mixture into the slow cooker and stir. Allow the stew a few more minutes to thicken.