Cut the sandwich rolls in half and generously spread the crumb with butter.
Heat a comal or griddle and toast the bread on all sides until crisp and gold.
Heat the cochinita in a small pan and set aside.
Spread the bottom half of the toasted rolls with refried beans. Then top the beans with the reheated pork.
Pile with pickled onions and avocado slices.
Close the sandwich with the other half and slightly press on top to keep the fillings on place.
Serve as it is or slice it in half for easier handle.
Notes
Choose the right bread: Select a bread that can handle the filling and avoid those with a super soft crumb (such as dinner rolls).
Reheating the meat: If you have a steamer, you can use it to reheat the pork. This method helps retain moisture and prevent drying. Just place the meat in a heatproof container or steamer tray and steam for 10-15 minutes, or until the pork is heated through.
Add spicy: If you like a bit of extra heat, consider adding habanero salsa or sliced jalapeños.