About store bought corned beef. Corned beef comes in two forms, ready to eat, and brined. Ready to eat corned beef is cured, then cooked, and usually packaged in slices or sliced at the deli counter. Do not use this! Brined corned beef is usually a hunk of brisket that has been cured in a salt solution and packaged in a hearty cryovac plastic bag with some of the brine. It has not been cooked yet. That's the stuff you want.