I've been eating Robins Pie and Mash in East Ham and Ilford for over 20 years and it doesn't have onions or mushrooms in the pie, it's got beef, water and probably some browning, nothing else. It's all to do with the pastry and the liquor.

The mash is just potato, nothing added. Everyone ponces the liquor recipe up and bases it on a Roux, but bear in mind East End Pie and Mash has been around for well over 100 years, this is basic cooking, nothing fancy!

But does it taste good, a unique taste with loads of vinegar all over it!!!

Try this for the liquor, ingredients in no particular order:
Arrowroot powder, water from the cooked spuds, mashed marrow fat peas, white pepper & salt, white vinegar, fresh parsley.