bread puddings an important category. Many desserts include bread whether in the form of breadcrumbs or pieces or slices of bread. There is also a whole class of desserts; see, to take only a few examples, queen’s pudding, poor knights of windsor, or summer pudding and certain types of charlotte and the like, where the role of bread is simply to line the recipient.
It is safe to assume that from the very distant past cooks have sometimes turned stale bread into a sweet pudding, if only by soaking it in milk, sweetening it by one means or another, and baking the result. The addition of some fat, preferably in the form of butter, and something like currants is all that is needed to move this frugal dish into the category of treats, and this is what has ensured its survival in the repertoire, even of cooks who never have stale bread on their hands.