Cytat: Michael_Corleone
Maybe the point is that the English don't perceive toast like a kind of sandwich but
only like a kind of bread, which is certainly uncountable
That's the secret.
Toast today is short for toasted bread. It denotes a material, just as steel, wood, ice-cream, beef, and many other substances.
When you order breakfast in an eatery, you might say, "…give me two eggs over easy on toast and coffee." Make note: "not on a toast." She could as well put the two eggs on one piece of toast aka toasted bread. There would be no complaint on my part, even though toast is today commonly made in some kind of pop-up contraption that accepts a certain slice size that cannot possibly accommodate two over easies.
But to make things more complicated for you, I will give you two contrary examples of absolutely correct (in my view) usages of the countable "toast." In (1), read what the mother says. In (2), guess the environment.
(1) Mother and child talk:
Child: May I have another toast, pleeeeeease?
Mother: Absolutely not.
Child: Why not?
Mother: Because you won't fit in the toaster.
(2) The macaroni-and-cheese left without paying; thwo egg toasts want more coffee. And hold the chicken.