Watch the video above to see Katharine McPhee and Sara Bareilles perform a beautiful, stripped-back duet version of “She Used to Be Mine” from Waitress the musical. Kat is currently starring in the show, which features music/lyrics by Sara, in London’s West End.

As a bonus treat, you can also see Katharine perform another song from the musical, “Bad Idea,” with her co-star, David Hunter!