Preheat the oven to 275 degrees.
Place brisket or corned beef in center of roasting pan.
Add 1-2 cups pickle juice, water, and Bay leaves to pan. You want the mixture to come about halfway up the height of the brisket.
Add mustard seed, coriander, peppercorns, MSG, and salt over the brisket.
Place butter on top of brisket.
Cover pan with foil.
Once brisket reaches around 195 degrees, remove foil from pan and continue roasting. Set the foil aside but don't throw it away. (This is a great time to start making roast potatoes & carrots if you're intending to.)
Roast until center of brisket is 225 degrees, around 6 hours.
Remove from pan, wrap in butcher paper, wrap in foil, and wrap in the kitchen towel.
Let rest for 30-45 minutes.
Unwrap from towel, foil, and butcher paper.
Slice and serve.