What is Pie n mash liquer?

It's likely a playful, made-up name referencing the traditional British dish "pie and mash".

Pie and Mash is a dish typically made with a meat pie, often containing beef, and served with mashed potatoes and a parsley sauce called "liquor".

If you're looking for a liqueur inspired by this dish, it's possible you're thinking of something else, or it's a local, informal invention.

Could you please provide more context? Perhaps you saw it on a menu or heard it mentioned in a conversation? Knowing more about where you encountered this term might help me figure out what you're looking for.