Corned Beef with butter

2 cups uncooked elbow macaroni 2 cups diced corned beef , cooked 3 cups finely chopped cabbage 3 tablespoons butter 1/2 cup chopped onion 3 garlic cloves ,[...]

2 large russet potatoes , peeled and cut into 1/2-inch cubes 1/2 teaspoon salt 1/4 teaspoon pepper 1/4 cup butter 1 large onion , chopped 8 ounces corned beef[...]