What is the slow song that goes laa laa la la - la la laa laa la la - la la laa - la la laa - la la laa?

It is sung by a girl and I think it is a newer song. It is a quiet song. I have heard it played when eating at P.F. Changs and Chili's twice, but I can never figure out the name of it. The girl almost sounds like Regina Spektor, but I can't find it on any of her songs. The majority of the song is the la la la part.