Well, 'in my day' (groan) just after the War, a casserole in England was (and still is in our house anyway) some meat (eg chicken quarters, or cheap-cut of lamb or stewing beef) put into a pot (ours is Pyrex). Add chopped onion, diced carrots, any other veg you may have, especially any that are getting a bit old like me. Add stock (a science in itself, but you can get a stock-cube nowadays) to cover, and a little salt and pepper. Add cubed potato or barley to thicken, put on the well-fitting lid and (most important) it must go in the oven on a very low heat for quite a long time. The beauty of it is, it can sit there in the oven for ages if the diners are late getting home. And reheated the next day it's even more tasty. I have been known to pop in a tiny spoonful of cooking sherry, but that's what my old mum would've called 'messing about with the food'. Post-War cooking was very simple and plain, since many things were still 'on the ration'.