Jellied eel at Cooke's in London.
Pie and mash is a traditional London working class food. Pie, mash and stewed eels shops have been in London since the 19th century and are still common in south and east London, in many parts of Essex and in places abroad, particularly Australia (see pie floater) - where there are significant expatriate communities.
The main dish sold is pie and mash — a minced beef and cold water pastry pie and mashed potato. It is common for the mashed potato to be spread around one side of the plate and for a type of parsley sauce to be present. This is commonly called eel liquor sauce or liquor (although it is non-alcoholic) because it is traditionally made using the water kept from the preparation of the stewed eels. The sauce traditionally has a green colour, which is not from food colouring, but from the parsley. Traditionally pie and mash shops have white tile walls, with marble floors, tables and work tops, which are easy to clean and give a Victorian appearance.
Jellied eels are another London speciality often sold in pie and mash shops. Chili-vinegar (vinegar containing pickled chilies) is also traditionally served with both of these dishes.
The pies, mashed potato and stewed eels are all prepared on the premises. Jellied eels are usually bought ready prepared. ( Wikipedia)