1. Preheat oven to 325 degrees Fahrenheit.
2. Place corned beef in a roasting pan, fat side up.
3. Arrange the cabbage, potatoes, carrots, onions, and garlic around the corned beef.
4. Pour the beef broth into the pan.
5. Spread the mustard over the top of the corned beef and sprinkle with pepper and thyme.
6. Cover with foil and bake for 3 hours.
7. Remove the foil and bake for an additional hour until the corned beef is tender.
8. Serve with boiled potatoes, cabbage, and carrots.