As a young child who grew up in a small neighborhood bakery, I had the privilege of making some special versions of our commercial goodies. One of which is biscocho, made from bread slices which were returned to us after not being sold for 3 days. When the regular ones are made with just one side of the bread slathered with a thin layer of margarine not quite covering the whole surface then coated with sugar, I made my own special batch (1 pan) of slices well covered with a thin layer of margarine on both sides, then coated with lots of sugar (I made sure sugar covers the whole area that had margarine). It was one of my favorite snacks.
One time I had craving, and it popped into my head to make some. I was with hubby then, and I asked him to try. He liked it and requested that I make some for him too, with a sprinkle of cinnamon after toasting (and he did not like it too toasted). Whoa! Another discovery for my hubby!
Then yesterday, my younger son was looking for something to eat, but he was getting tired of the usual pan de pizza that we make using homemade pizza sauce, slices of ham or pepperoni, and mozzarella cheese. I thought of offering to make biscocho for him. He was not sure what it was but he was ready for a new kind of delight. He was not disappointed, and he asked that I make some for his breakfast today. So I made some for both my sons, and the older one told me I should have doubled his share. But I have used up all the bread slices. I told him I would get more next time I go to the grocery store.
I usually use stale bread or hotdog rolls for this purpose, and the oven toaster. I watch carefully as I bake, because if I overdo it, the caramelized sugar burns and gets bitter. I also want to cool it down a bit before biting to it, as the caramelized sugar can be very very hot.
Don't be tempted to use a thick layer of butter or margarine, as this will only get the bread soggy, then you won't get the crunchy result that you want. A thin layer is enough, and you won't get disappointed with the crunch and the taste.
I think the best tasting biscocho would be one that is made from leftover sponge cake (but who would have leftover sponge cakes? They are too good freshly baked!)