If you’re a lucky ticket holder for the any of the Back Bay Chorale’s performances of Beethoven’s Missa Solemnis at the Sanders Theater, the ladies of UpStairs on the Square have another treat in store for you – they’re offering special prix fixe dinners in both dining rooms. From Friday, May 19th through Sunday, May 21st concert-goers can duck in for an early prix fixe dinner (at 5:30, 6:00 or 6:30pm) from chef Steven Brand. Dinner in the Soiree Room costs $45 per person, while dinner in the Monday Club Bar costs $35 per person. Call UpStairs on the Square at 617.864.1933 to make reservations – just ask for the special Missa Solemnis menu.