Pie and mash

Pie and mash is a traditional working-class food, originating in the Docks of London. Often accompanied with jellied eels, the dish has been popularised as "a Cockney classic". It typically consists of a minced beef pie, mashed potato, and a parsley sauce known as liquor. Pie, mash and eel shops have been in London since the 19th century, and are still common in East and South London, and in many parts of Kent and Essex. During the Victorian era, industrial air pollution tended to be worse in the east and southeast of London because of the prevailing westerly wind, with the result that the East End was settled more by the working classes, while the western part of the city was home to higher social classes.

Source: Wikipedia