I do not eat mussels myself, so I don't know who on Orient might offer that. I personally really enjoy Kakao. They have a varied menu, from french favorites, to wonderful pizza, to burgers. And I really enjoy the little individual dining areas, where you can eat without being right on top of your neighbor.
As far as mussels in particular, since you stay in P'burg, have you tried the mussels at Mark's?? People who like mussels rave about them!