Puzzler #1: Can you pie-dentify this?

The lyrics below are from a Broadway musical considered to be a "bloody brilliant" masterpiece. Can you name it and its composer, and the character who sings the song?

Mrs. Mooney has a pie shop...

Does a business, but I've noticed something weird -

Lately all her neighbor's cats have disappeared...

Wouldn't do in my shop.

Just the thought of it's enough to make you sick.

And I'm tellin' you, them pussy cats is quick.....

Answer

Mrs. Lovett sings these lines in The Worst Pies in London from Act I of Sweeney Todd by Stephen Sondheim. C'mon, you knew that, right?