Pre heat oven at 375°F.
In a medium bowl, combine butter with Parmesan cheese, breadcrumbs, shallots, garlic and parsley.
Arrange frozen mussels facing up on a baking tray and top each mussel with the butter-cheese mixture.
Bake for about 20 minutes until cheese melts and the top of the mussels looks golden brown.
Garnish with more parsley and lemon wedges.