Today in London.

Pie and mash, at Wikipedia:

The main dish sold is pie and mash — a minced beef and cold water pastry pie served with 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 simply liquor (although it is non-alcoholic), traditionally made using the water kept from the preparation of the stewed eels. The sauce traditionally has a green colour, from the parsley.[1] Sometimes a gravy is served instead (normally oxtail or Bisto).