In a medium saucepan, heat butter until melted over medium-high heat. Add bacon and cook for 2 minutes. Stir in shallots and cook for 1 minute. Add mussels and cider and bring to a boil. Cook, covered, for 2 minutes. Stir in cheese, reduce heat to medium and cook until mussels are open, about 2 minutes more. Stir in parsley. Serve immediately.