I brushed the cooked brisket with yellow mustard before broiling. Use the mustard of your choice. Corned beef is easier to slice after it's cold. If you want thin slices, you need to cook the brisket in advance with enough time to place in the refrigerator for at least an hour before slicing. If you want corned beef for dinner tonight and sandwiches the following day, cook two, have one for dinner and place the other in the refrigerator overnight.