Preheat the oven to 325 degrees.

Unwrap the corned beef brisket and place it fat side up in a baking dish.

If a spice packet is included, sprinkle it over the brisket.

Sprinkle ground black pepper and rub it in.

Cover the dish tightly with heavy aluminum foil.

Bake in the preheated oven for 2 1/2 hours.

Remove the foil and continue baking for 1/2 hour to 45 minutes.

Check the brisket for doneness by inserting a fork; it should go in easily.

If the brisket is tough, bake for another 30 minutes to 1 hour until fork-tender.

Remove the brisket from the oven and let it rest, covered loosely with foil.

While the brisket is resting, prepare the balsamic reduction.

Combine balsamic vinegar and sugar in a small saucepan over medium-high heat.

Stir and bring to a boil, then reduce heat to medium-low.

Simmer until the mixture is reduced by half and thickened.

Set the balsamic reduction aside.

Raise the oven temperature to 350 degrees.

Cut the green cabbage into 8 wedges.

Heat olive oil in a large, heavy skillet over medium-high heat.

Add the cabbage wedges and sear on both sides until browned, about 1 minute per side.

Transfer the seared cabbage to a rack placed over a baking sheet.

Sprinkle the cabbage pieces with salt and pepper.

Pour Guinness (or other beer) into the bottom of the skillet.

Carefully transfer the skillet to the oven.

Bake the cabbage for 20 minutes, or until tender and deep brown.

Slice or shred the rested corned beef on a cutting board.

Place the sliced beef on a large platter with the cabbage wedges.

Drizzle generous spoons of balsamic reduction over the cabbage slices.

Serve the corned beef next to the cabbage.

Serve with a dish of grainy mustard.

Serve with boiled new potatoes.

Shred leftover corned beef with two forks if you prefer that consistency!

Make a leftover corned beef sandwich with a slice of brisket and a wedge of cabbage on rye.