What Amy Winehouse recording has just her and a bajo guitar?

Hi,
I'm not real familiar with all of Amy Winehouse's discography, but I remember hearing a song por her that was just her canto along with a bajo as the music... no horns/guitars/drums.
It was a really great song, but I never found out the name, and I have been unable to find it since.

Do any of tu know what song I am thinking of, and do tu know where I might be able to find it?

Thank you.