Place brisket in a large dutch oven or stock pot.
Season with spice packet, bay leaves, coriander seed, mustard seed, salt and pepper.
Cover with water. You can also use a combination of beef broth and a bottle of Guinness.
Bring to a boil; reduce heat, cover, and simmer for 2 hours.
Add potatoes and carrots and return to a boil.
Reduce heat to a simmer; cook covered for about 30 minutes, or just until beef and vegetables are tender.
Add onions and cabbage to the pot and return to a boil.
Reduce heat to a simmer, cover, and cook for about 15 minutes, or until onions and cabbage are tender.
Remove from heat and serve warm.