Grilled Cabbage and Corned Beef Wedge Salad

Name: Grilled Cabbage and Corned Beef Wedge Salad
Ingredients: 4 very thin slices corned beef from the supermarket deli; 1/2 head green cabbage (from a 3-pound cabbage), cut into 3 wedges, cores intact; 3 tablespoons extra-virgin olive oil, plus more for drizzling; Kosher salt and freshly ground black pepper; 1/2 cup buttermilk; 1/4 cup mayonnaise; 1 tablespoon horseradish; 1 tablespoon whole-grain mustard; 1/2 cup parsley leaves; 1/2 teaspoon cider vinegar, or more to taste; 1 medium carrot, shredded (1/2 cup); 1 scallion, sliced