Pie and Mash 

1. A very popular 'old school' dish in London, namely the East End. Consists of a Pie containing just Minced Beef and a serving of Mashed Potato. Commonly covered with 'Liquor' (Pronounced 'Licker'), which is an almost flavourless sauce consisting of flour, water and parsley.

2. Cockney rhyming slang for 'Slash', meaning to urinate.

3. A slang term for 'Gash' referring to the female genitalia. Although in this case, it is used to refer to any type of sexual contact with a partner, not just 'Gash'

1: Lets go to the Pie and Mash shop for lunch.

2: I can't hold it any more, I'm going for a Pie and Mash.

3:
Guy: I went and saw my girlfriend last night.

Friend: Sweet, did you get any pie and mash?

Pie and Mash by MJBoy February 25, 2009

pie and mash 

cockney rhyming slang for slash (to urinate)

i'm gonna go take a pie n' mash

pie and mash by ben curry September 24, 2003

pie and mash 

London, UK.
Historically, the pies were made from scraps of beef and vegetables, leftovers or from the local markets, under a pastry crust. The mashed potatoes were liberally covered in parsley gravy or "liquor". There has been a great revival in these dishes and quite a number of Pie ‘n’ Mash restaurants can now be found across London.

Traditional foods in London include pie 'n' mash and jellied eels.

pie and mash by Blue Cawdrey November 22, 2004