Sort, scrape, wash the mussels, discarding any that do not close.
Steam them in a cup of water, in a large kettle. Drain mussels. Remove the empty half shell from each mussel, and discard, leaving the mussel attached to other half shell.
Peel and finely chop shallots and garlic. Chop the parsley.
Cut the butter into small pieces, and mix well with breadcrumbs, shallot, garlic, parsley and pepper.
Fill each mussel with the stuffing.
Arrange in a baking dish, and broil until brown. Garnish with parsley and serve at once.