Preheat the oven to 325 degrees F. Unwrap the brisket and place it fat-side up in a large baking dish.

If the brisket came with a spice packet, sprinkle it over the top, then sprinkle on 3 tablespoons pepper and rub it in.

Cover the dish with heavy-duty foil and bake for 2 1/2 hours, then uncover and continue baking until the brisket is very, very tender (almost falling apart!) and a fork inserted into the meat goes in easily, about 1 more hour.

Remove from the oven and cover loosely with foil to keep warm and let rest 20 minutes.

Increase the oven temperature to 400 degrees.

Cut the cabbage into 8 wedges, Working in two batches if necessary, heat the olive oil in a large heavy skillet over medium-high heat.

Add the cabbage and sear on both cut sides until the cabbage gets as much color as possible, about 1 minute per side.

Use a spatula to transfer the cabbage to a rack placed on a rimmed baking sheet.

Season with Mikes SPG Seasoning

Pour the Guinness into the bottom of the pan, then carefully transfer to the oven. Bake the cabbage until tender and deep brown, about 20 minutes.

Drizzle the balsamic all over the top (do not mix) and bake another 10 minutes (watching so balsamic doesn't burn)

Slice the corned beef and place it on a platter with the cabbage.

Optional: Drizzle more balsamic all over the cabbage for more flavor..