Corned Beef and Cabbage with Horseradish Cream Sauce

Name: Corned Beef and Cabbage with Horseradish Cream Sauce
Prep time: 20 min
Cook time: 180 min
Total time: 200 min
Yield: 6 - 8
Ingredients: For the Corned Beef and Vegetables:; 1 (4-lb) flat-cut corned beef with seasoning packet (do not trim the fat); 4 tablespoons unsalted butter, melted; 2 tablespoons prepared horseradish; 1½ teaspoons salt; ¼ teaspoon ground black pepper; 6 medium carrots, cut into 2-in chunks; 1¼ lb small gold potatoes (about 2.5" in diameter), halved; 1 very small green cabbage, cored and cut into ½-inch-thick slices (see note); 2 tablespoons chopped Italian parsley, for garnish (optional); For the Horseradish Cream Sauce:; 1 cup sour cream; 2 tablespoons prepared horseradish, plus more to taste; 1 tablespoon Dijon mustard; 1 teaspoon white wine vinegar; ¼ teaspoon salt; ¼ teaspoon ground black pepper; ¼ teaspoon sugar