Technically, this casserole is a stew because it's cooked on the stovetop. A true casserole is baked in the oven and is more suited to things that need a very long cooking time. There's no fixed recipe for this dish - people will use whatever sausages they prefer, their own choice of beans and any additional vegetables. But whatever's in it, it's a proper winter warmer and easy to make.
Sunflower oil for sautéeing.