Corned Beef and Cabbage

Place corned beef, thyme, coriander, and bay leaves in a large (about 10-quart) Dutch oven; add cold water to cover by 1 inch (10 to 12 cups). Bring to a simmer over medium-high; reduce heat to medium and cook, partially covered, skimming foam occasionally, until beef is fork-tender, about 2 hours.

Add cabbage, potatoes, carrots, turnips, 1 1/2 teaspoons of the salt, and 1/2 teaspoon of the pepper to beef mixture. Increase heat to medium-high; cook, partially covered, until vegetables are al dente, 25 to 30 minutes. Remove from heat; let stand, covered, until vegetables are fork-tender, about 10 minutes.

Meanwhile, stir together sour cream, parsley, whole-grain mustard, Dijon mustard, Worcestershire sauce, and remaining 1/2 teaspoon salt and 1/4 teaspoon pepper in a small bowl. Set aside.

Transfer corned beef to a cutting board; slice against the grain into 1/2-inch-thick slices. Transfer to a platter. Using a slotted spoon; transfer vegetables to platter, discarding bay leaves and thyme sprigs. Spoon 1/4 cup cooking liquid over beef and vegetables. Garnish with additional parsley and serve with mustard sauce.