Baked Corned Beef and Cabbage Hash
1 wedge leftover cooked cabbage
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
Heat oven to 375 degrees F. If using fresh cabbage, bring a small pot of water to a boil. Add 2 teaspoons salt and the cabbage and cook for 5 minutes; drain and squeeze out any excess moisture.
Heat the oil in a large skillet over medium heat. Add the onion and 1/4 teaspoon each salt and pepper and cook, covered, stirring occasionally, until tender, 8 to 10 minutes. Add the corned beef and garlic and cook, stirring occasionally, for 4 minutes. Remove from heat and fold in the cabbage and parsley.
Coat a deep 8- by 8-inch square baking dish with oil. In a bowl, whisk together the heavy cream and mustard.
Lay a third of the potatoes in the baking dish, slightly overlapping them. Top with a third of the corned beef and cabbage mixture (about 1 cup) and sprinkle with a third of the cheese (about 1/3 cup); repeat once. Top with a last layer of potatoes and cabbage mixture. Pour the cream mixture into the dish.
Cover the baking dish with foil, place on a rimmed baking sheet and bake for 45 minutes. Uncover, sprinkle with the remaining cheese, and bake until the potatoes are tender and the top is golden brown, 25 to 30 minutes more. Let rest for 10 minutes before serving.