1In a large bowl, soak the mussels in cold salted water for 30 minutes; rinse and scrape off the beards (the hairy tuft protruding from one side of the shell).
2In a large, deep skillet or saute pan, melt the margarine. Saute the shallots and garlic until tender, about 5 minutes. Add the wine, broth, and pepper; bring to a boil. Simmer, uncovered, 5 minutes. Drain the mussels and add to the pan; cover and cook until the mussels are fully open, about 8 minutes, shaking the pan frequently. Discard any mussels that do not open.
3Divide the mussels and broth among 4 deep soup bowls; sprinkle with parsley.