The actor will soon take up his usual place opposite Mulligan for the second, no...fourth time…in Skylight.
The Broadway dame will discuss her life and career in a one-night-only San Francisco engagement.
The New York premiere of Andrew Lippa's oratorio will play Lincoln Center on October 6.
Lansbury will be joined by cast members from the 2009 Broadway revival and 2014 West End productions of Noël Coward's comedy.
The evening will take place before the release of the new film adaptation of the musical.
The actor-singer is playing 54 Below on Sundays before the Broadway debut of Beautiful — The Carole King Musical, in which he stars.