Chip Buttie!

Dear LHL

My friend and I are having a dispute only you can settle. A chip sandwich in north east Lancs is, I contest, called a chip butty. My friend has a somewhat unbalanced approach to the discussion and she claims that most Lancastrains call just such a sandwich, a chip sarnie. As LHL appears an authority on all things Lancastrian can you Please inform who is correct? Thank you.

Angela, Colne