re: The Mother-in-Law. My sister and I had tamal tortas in Tlaxcala. It was early morning outside the market and there was a lady with a huge steaming pot, piles of bread and lots of customers. We asked what she was selling and she said tamal sandwiches. In my adorably dense way, I asked what that was and got a chorus of "a tamal on bread!" from the customers.
The vendor would slit a telera , deftly unwrap a steaming tamal and empty it onto the bread. She adorned it with sauce, wrapped the bottom half in a napkin and presented it to the waiting customer.
Since a telera is a fairly dense bread and since a tamal is essentially steamed corn dough, we were expecting a gummy mass. What a nice surprise! The two items somehow melded into a new and wonderful foodstuff that was extremely delicious and -- no surprise -- very filling.