Corned Beef Dinner for St. Patrick's Day

Step 1
Make the corned beef and vegetables: Place corned beef into a 6-quart Dutch oven, and pour in enough water to cover by 2 inches. Bring to a boil, skimming the liquid occasionally to remove fat from the top. Reduce the heat to medium-low, cover, and simmer for 2 hours.

Step 2
Arrange cabbage, potatoes, onions, and carrots around beef; return to a boil. Reduce the heat to medium-low, cover, and simmer until vegetables are tender and beef can easily be pulled apart with a fork, about 40 minutes. Transfer beef to a serving platter. Remove vegetables with a slotted spoon and arrange around beef. Reserve 1 1/2 cups cooking liquid for the sauce.

Step 3
Make the sauce: Melt butter in a small saucepan over medium heat. Whisk flour into melted butter until dissolved and bubbling, about 1 minute. Add reserved cooking liquid and vinegar; cook, stirring frequently, until sauce is slightly thickened, about 4 minutes. Remove from the heat and whisk in sour cream and mustard.

Step 4
Serve sauce alongside corned beef and vegetables.