Take your corned beef out of the packet it is in, and rinse it thoroughly. You will not use the brine that it has been sitting in, so discard that. Put the corned beef in a large, heavy pot and add enough COLD water to cover the corned beef by one inch. Add all of the remaining ingredients. Bring to a boil and skim all the foam that rises to the surface.
Lower the heat to a simmer. Put the lid on the pot. Cook, turning every 30 minutes or so, for about 3 to 4 hours. At 3 hours, start to check tenderness every 15 minutes with a fork. When it's perfectly tender, you should be able to stick a fork or a thin knife into the corned beef very easily. Remove the corned beef from the liquid to a cutting board.
Serve, slicing across the grain. Or wrap it carefully in aluminum foil and refrigerate for up to 2 days; reheat at 300°F for 30 minutes in the foil; unwrap and heat about 15 minutes more.)
Notes
If a spice packet is not included with the corned beef, you can combine the following to add to your simmering corned beef: