01 -
Heat a large 12-inch skillet over medium-high heat for at least 2 minutes. Open the package of corned beef and drain the brine. There is no need to rinse the meat. Save any included spice packet.
02 -
Add oil to the hot skillet until it shimmers. Add the drained corned beef and sear for 2-4 minutes on each side until golden brown, flipping carefully with tongs.
03 -
Transfer the seared corned beef to the slow cooker, fat side up. In the same skillet, combine beef broth with whole grain mustard. Bring to a bubble while scraping up the browned bits from the pan. Pour this mixture over the corned beef.
04 -
Add the smashed garlic cloves, onion wedges, peppercorns, thyme, and bay leaves to the slow cooker, tucking them into the liquid. Sprinkle the reserved spice packet over everything.
05 -
Cover with the lid and cook on low for 6-7 hours.
06 -
Prepare the carrots by peeling and cutting them into thirds, slicing larger segments in half lengthwise. Add the carrots on top of the beef, cover again and cook for another 1-2 hours.
07 -
Slice the cabbage in half, remove the stem, and cut into large wedges. Melt butter in a 12-inch skillet over medium-high heat. Add all the cabbage and sprinkle with kosher salt. Sauté for about 10 minutes until slightly wilted but still firm.
08 -
Add the sautéed cabbage on top of the carrots in the slow cooker. Continue cooking on low for another 30-60 minutes, until the cabbage is softened and has absorbed the corned beef flavor.
09 -
While the cabbage cooks, roast the red potatoes in the oven separately for best texture and flavor.
10 -
Remove the corned beef to a cutting board and let rest for about 10 minutes. Slice against the grain into serving portions.
11 -
Arrange the components on a large platter: drained cabbage, carrots, sliced corned beef, and roasted potatoes. Garnish with chopped parsley and chives.
12 -
Serve with homemade horseradish sauce on the side.