Preheat oven to 350°F. Place a very large sheet of aluminum foil over a baking sheet. Set several paper towels over the aluminum foil. Rinse the roast and discard the seasoning packet. Pat the roast dry with the waiting paper towels. Discard the paper towels and place the corned beef, fat side up, on the dry foil.

Stir together the honey and the mustard. Reserve ¼ cup of the sauce in a separate dish and pour the remaining sauce over the top of the corned beef. Sprinkle the brown sugar evenly over the top of the roast.

Wrap the beef very loosely with the foil, tenting it and allowing space between the top and sides of the meat and the foil. Bake for 2 hours.

Remove from the oven, and change the temperature to Broil. Open the foil and place the roast back in the oven. Broil for just 3-4 minutes, until the top is lightly browned and bubbling. Watch closely while broiling, it will burn very quickly once it has browned!

Allow the corned beef to rest for at least 10 minutes before slicing across the grain of the meat. Serve with the reserved honey mustard sauce.