Prepare the brine: In a large pot, combine the kosher salt, sugar, peppercorns, mustard seeds, coriander seeds, red pepper flakes, garlic, onion, bay leaves, ginger, and allspice. Add 8 cups of water and bring to a boil, stirring until the salt and sugar dissolve. Reduce the heat and simmer for 10-15 minutes to infuse the spices.
Brine the beef: Once the brine has cooled to room temperature, place the beef brisket in a large bowl or a resealable bag. Pour the brine over the brisket, ensuring it’s fully submerged. Refrigerate for 3-5 days, turning the meat occasionally.
Cook the corned beef: After the brining period, remove the brisket from the brine and rinse it under cold water. In a large pot or Dutch oven, place the brisket and cover it with water. Bring to a boil, then reduce to a simmer. Cook for 3-4 hours, or until the meat is tender and can easily be shredded with a fork.
Serve: Once the corned beef is cooked, remove it from the pot and let it rest for 10 minutes before slicing thinly against the grain. Serve with your favorite sides or as a sandwich.
