Proceed exactly the same as for oyster sauce, using only the liquor of the mussels (not the beards) instead of the oysters, and serving the mussels in the sauce.
Original Text
279. Mussel Sauce.—Proceed exactly the same as for oyster sauce, using only the liquor of the mussels (not the beards) instead of the oysters, and serving the mussels in the sauce; about four dozen would be sufficient.