Preheat your oven to 300°F (150°C).
Place the corned beef brisket into the Dutch oven. Pour the beef broth over the brisket, ensuring that it is at least halfway submerged.
Add apple cider vinegar, whole grain mustard, minced garlic, onion quarters, pickling spice, bay leaves, salt, and black pepper to the Dutch oven.
Cover the Dutch oven with its lid and place it in the preheated oven. Cook the corned beef for approximately 2.5 hours, or until it is tender when pierced with a fork.
Remove the Dutch oven from the oven and add the cabbage wedges around the brisket. If necessary, add more beef broth or water to ensure the liquid level remains consistent.
Return the Dutch oven to the oven, with the lid on, and cook for an additional 30 minutes, or until the cabbage is tender but not overcooked.
Once the cabbage is cooked to your liking, carefully remove the Dutch oven from the oven and let it sit for a few minutes with the lid off.
Transfer the corned beef to a cutting board and slice against the grain into thin slices.
Serve the sliced corned beef alongside the tender cabbage wedges. Garnish with fresh parsley if desired.