Items you will need
Large pot or large roaster oven
Watch or kitchen timer
Large cuts of corned beef -- 10 to 12 pounds -- typically include the whole brisket, the leaner flat cut and the fattier point cut. Since corned beef usually loses between 25 to 40 percent of its weight during cooking, mostly due to the injected brine that cures the beef during processing, you will serve a far smaller brisket than you bought. Brisket is a tough cut of meat and retains its flavor and texture best when allowed to simmer very slowly for a long period of time at very low temperatures. You can add vegetables such as potatoes, parsnips, cabbage or carrots to your meat during the last half of cooking time.
Cut the whole brisket into two pieces by slicing it across the layer of fat that separates the two cuts. Place both pieces into a large pot. Add water to completely cover the brisket.
Add seasonings to the water, if you are cooking from a recipe that calls for additional seasoning. Use the seasoning packet that came with the beef or add seasonings according to your recipe.
Set the stovetop burner to high heat. Leave the pot uncovered while you bring the corned beef to a boil.
Reduce heat to very low or simmer immediately after the brisket begins to boil.
Cover and simmer the meat for approximately 1 hour per pound. Brisket is done when fork-tender. Remove the meat from the hot liquid immediately and transfer it to a warm plate.
Put your corned beef, lean side down, into a 12-to-18-quart roaster oven preheated to 325 degrees Fahrenheit. Fill roaster with water to a level one-half to two-thirds of the height of the brisket.
Sprinkle seasonings into the roaster oven, if desired. Cover the brisket and set the timer for 10 minutes.
After 10 minutes, reset the roaster oven temperature to 250 F. Cook for 1 hour per pound or until meat is fork-tender. Remove the meat from the hot liquid immediately and transfer it to a warm plate.
Most corned beef is sold as a pre-cured and seasoned meat, with an accompanying seasoning packet. If curing your 10-pound corned beef at home, you can create your own seasonings using kosher salt, saltpeter, brown sugar, peppercorns, yellow mustard seeds, whole coriander seeds, allspice berries, whole cloves, ground ginger and bay leaves. Smear the mixture over the brisket until the beef is completely covered. Place the seasoned brisket in a freezer bag, press out as much air as possible and place it in the back of the refrigerator for one week, turning the bag over every day. Cold-water rinse the spices off the brisket before cooking.
Higher cooking heat and faster cook times will likely leave you with a brisket that’s tough to chew. Always leave yourself enough time to cook corned beef low and slow.