Bangers and mash are a public house classic, some fatty sausages with buttery potatoes perfect for soaking up an afternoon's worth of ale. An inexpensive way to fill up your stomach, the classic cheap banger has given way to today's gastropubs replacing the fatty pork sausage with anything from spiced lamb to chicken-and-apple adaptations of the classic—although you can still find classic versions of this popular dish throughout Britain as a mainstay of pub menus.
Onion gravy is the simple sauce that normally tops the pile of sausage and mash. There are many versions of this gravy but the most important part of this simple sauce is making sure your onions are a deep even brown with no scorching. There is no real secret on how to properly cook up your onions; just keep an eye on them and toss them often to make sure they cook evenly.
Once you've figured out your onions it's a matter of stock. I've called for beef stock in this recipe, but if you have some good chicken or even vegetable stock, use that instead. Just keep in mind that using a vegetable stock with result in a thinner final gravy.
Finding some proper bangers can be challenging depending on where you are living. If your area has a good butcher, that's always a good place to start when searching out sausages. If, after much searching, you find yourself without bangers (and without the proper equipment to make a batch yourself), then in a pinch substitute any sort of plain, fatty pork sausage. Bratwurst always seems closer to a proper banger than a mild Italian sausage in my mind. But use your own judgement.