Prep. Place the corned beef brisket in a large Dutch oven or stock pot. Season it with the spice packet it came with and add in the bay leaves, coriander seed, mustard seed, salt, and pepper.
Add the liquids. Cover the brisket with water. You can also use a combination of beef broth and a bottle of Guinness.
Cook. Bring the mixture to a boil, then reduce the heat, cover, and simmer for 2 hours.
Add vegetables and continue to cook. Add potatoes and carrots and return to a boil. Then, reduce the heat to a simmer; cook covered for about 30 minutes, or just until the corned beef and vegetables are tender.
Add remaining ingredients. Stir in the 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 the onions and cabbage are tender.
Serve. Remove the beef from the heat and let it rest for 10 minutes. Serve warm.
Notes
Keep it low and slow. Corned beef is a tough cut, so cook it on low for the juiciest, most tender results.
Try beer! Swap some of the cooking liquid for beef broth and Guinness for extra Irish flair.
Watch the water. Check every 40 minutes and add more liquid if needed.