Place brisket in a pot and cover with water. Add peppercorns and bay leaves and bring to a simmer. Cook for 3 to 3 1/2 hours until fork tender, Set aside and make glaze.
Glaze
Drain corned beef and place on a foiled baking sheet. Preheat oven to 350 degrees F.
In a bowl, mix together sugar, soy sauce, mustard, ginger, ketchup, pepper flakes and molasses. Brush brisket with glaze. Bake for 15 to 20 minutes, re-glazing two times while baking.
Refrigerate overnight and slice across the grain very thin for sandwiches.