Put the brisket into a saucepan with the carrots, onions, mustard and the herbs. Cover with cold water, and bring gently to a boil. Simmer, covered, for 2 hours. Discard the outer leaves of the cabbage, cut in quarters and add to the pot. Cook for a further 1 to 2 hours or until the meat and vegetables are soft and tender.
Serve the corned beef in slices, surrounded by the vegetables and cooking liquid. Serve with lots of floury potatoes and freshly made mustard.