Scrubbed mussel shells with a stiff brush, wash well. Place shells in a kettle with wine, scallion, parsley, garlic, bay leaf, thyme and pepper. Cover kettle tightly and cook over high heat until shells open, about 5 minutes. Remove mussels from the kettle. Take off top shells and place mussels in a deep heated dish or tureen. Strain stock and cook over high flame until reduced by one third its original quantity. Add butter and salt to taste; heat through. Pour over mussels in tureen. Add chopped parsley for garnish. Serve in deep soup plates or small casseroles and eat the mussels directly from the shell. Serves 4 to 6. Formatted by Mary Wilson, BWVB02B.