This slow-cooker chuck roast is winter comfort food at its finest. A bright, slightly sweet sauce balances the rich and tender braised beef. You can substitute multi-colored baby potatoes (halved) for the Yukon variety and fresh fennel fronds for the parsley, if desired.
Sprinkle the roast with 1 teaspoon of the salt. Heat the oil in a large skillet over medium-high; add the roast, and cook until browned, about 4 minutes on each side. Transfer the roast to a 5- to 6-quart slow cooker. Place the carrots, potatoes, and cabbage on and around the roast.
Stir together the beef stock, vinegar, brown sugar, mustard, garlic, pepper, and remaining 1/2 teaspoon salt in a bowl, and pour the mixture over the vegetables and roast. Cover and cook on LOW until the roast and vegetables are tender, about 9 hours. Turn off the slow cooker, and remove the roast, reserving the cooking liquid and vegetables in the slow cooker. Cover the slow cooker to keep the cooking liquid and the vegetables warm. Let the roast rest 20 minutes; slice the roast across the grain. Remove the cabbage from the slow cooker, and cut the cabbage into slices. Place the cabbage, potatoes, and carrots on a serving platter; top with the sliced meat. Sprinkle with the parsley, and serve with the reserved cooking liquid.