Heat the olive oil in a large pot over medium heat. Add the ground beef and cook until browned, breaking it up with a spoon as it cooks.
Stir in the onion and garlic. Cook for 3 minutes until the onion softens.
Add the Dijon mustard and thyme. Stir everything together for 1 minute so the mustard coats the beef.
Pour in the beef broth. Add the potatoes, parsnips, and carrots. Season with salt and pepper.
Bring the stew to a boil, then lower the heat and simmer uncovered for 25 minutes. Stir occasionally until the vegetables are tender.
Taste and adjust salt or pepper if needed. Ladle into bowls and top with fresh parsley.