Baked Corned Beef and Cabbage Hash

Name: Baked Corned Beef and Cabbage Hash
Prep time: 30 min
Total time: 30 min
Cuisine: American
Ingredients: 1 wedge leftover cooked cabbage; Kosher salt; Pepper; 2 tbsp. olive oil; 1 medium onion, chopped; 8 oz. leftover sliced or deli corned beef; 1 clove garlic, finely chopped; 1/2 c. chopped fresh flat-leaf parsley; 1 c. heavy cream; 1 tbsp. Dijon mustard; 1 lb. russet potatoes, sliced; 6 oz. Gruyère cheese, grated