After having a near-religious experience while recording “At the Ballet†with Anne Hathaway and Daisy Ridley, and channeling some Austrian nuns with Jamie Foxx for “Climb Ev’ry Mountain,†Barbra Streisand released on Sunday a video of her and Alec Baldwin singing “The Best Thing That Has Ever Happened.†In the video, which is a behind-the-scenes sneak peek at Streisand’s new celebrity-duet album Encore: Movie Partners Sing Broadway, Babs explains how important it was for her to tap a real “New Yawker†to cover this Stephen Sondheim number. As to be expected, Baldwin used his silky voice to give his best impersonation of a Rat Pack–type for the occasion. Somewhere in an alternate universe, Jack Donaghy is toasting the air as he tips his perfect head of hair forward in approval.