You can make tortilla chips without frying them. Just heat them up slowly and the tortilla will become hard as a tortilla chip. Have used this method to make tostadas.

I'm sure the Mexicas knew of this back then. Leave them too long in a hot surface and they become tostadas. Break them manually and now you have tortilla chips!

Uh, this is odd. Tostadas in Spain means the classical toasted bread slices, either on a toaster or a pan.