Preheat your oven to 325°F (163°C). Time to let that Dutch oven shine!
In your Dutch oven, melt the butter over medium-high heat. Sear the corned beef brisket for about 2–3 minutes per side, just until you get that lovely golden edge.
Pour in the broth or water. Add the onion, garlic, peppercorns, dried thyme, bay leaves, and that spice packet. Give it a gentle stir, pop the lid on, and slide it into the oven.
Let it bake for 2½ hours while you do something fun—play a little bridge, read a book, or call your sister.
Carefully take the pot out (it’s gonna smell amazing already!). Nestle the carrots and potatoes around the beef. Cover it back up and return it to the oven for another 30 minutes.
Add in the cabbage wedges, snuggling them in with everything else. This time, keep the lid off and bake for another 20 to 30 minutes so the cabbage gets nice and tender and a little golden on top.
Remove the brisket and let it rest on a cutting board for about 10 minutes. Slice it up against the grain—trust me, it makes all the difference!
Serve everything up on a big platter, ladle over some of that cozy broth, and enjoy a good, hearty meal that feels like a warm hug from your kitchen.