I have never heard of these cakes either. I had to bake with my mother on a Saturday, a sandwich cake, some iced buns and maybe an apple pie for Sunday, the only day we had a pudding. I remember occasionally baking jam tarts and lemon meringue pie with the filling from one of those packets.
When relatives came to visit, maybe a couple of times a year she would buy cakes which we were not allowed to ask for. If they did not want them we could have one. Oh the bliss of chocolate eclairs, meringues or cream horns. I think the said relatives often sensed our collective will that forced them not to eat the cakes!!