We call those sandwiches guajolotes [*]; they are specific to to Tulancingo.
One of the typical foods of the Tulancingo region are los guajolotes: buns (similar to a white bread baguette) are halved, filled with refried beans, cheese enchiladas, onions, and salsa. Guajolotes may also sometimes include meat, such as: shredded chicken, ham, sausage, or other delicacies. The assembled sandwich is then pan-fried in butter or oil. [**]
Here is a youtube video of one being made.
* Direct translation: turkeys
** Roughly translated from wikipedia: Tulancingo de Bravo