For the corned beef:
3 pounds corned beef (in bag with seasoning packet)
¼ cup grainy dijon mustard
3 tablespoons prepared horseradish
For the cabbage:
1 head cabbage
2 tablespoons olive oil
2 tablespoons minced garlic
1 teaspoon salt
1 teaspoon ground black pepper
Remove the corned beef from the bag. Rinse the meat very well under cold water and pat very dry with paper towels. Save the spice bag. Set aside.
Place 2 large sheets of aluminum foil on a flat surface crisscross.
Lay the corned beef in the middle of the foil.
Rub all sides with the mustard and horseradish.
Place the meat with the fat side up.
Sprinkle the spice packet over the top.
Wrap the foil around the corned beef and place on a rimmed baking sheet.
Bake in the preheated oven for about 1-hour, 15 minutes.
Meanwhile, cut the bottom off of the cabbage and set the flat end on a cutting board. Cut the cabbage into slices about 1-inch thick.
Arrange the slices on a single layer on a rimmed baking sheet.
In a small bowl, mix together the garlic, salt, and pepper.
Season the cabbage slices with the garlic mixture.
Drizzle the olive oil over the steaks.
Cover tightly with aluminum foil.
When the corned beef has baked for the above time, slide the cabbage into the oven on another shelf. Do not remove the corned beef.
Continue baking for 45 minutes to 1-hour.
Open the oven and remove the foil on both baking sheets and continue baking for another 15 minutes.
Turn the oven off and remove the meat. Allow the cabbage to remain in the oven to keep warm.
Let the meat rest for a few minutes, then cut the meat at a diagonal across the grain into thin slices.
Serve hot alongside the cabbage.