There are different bread options, there are many different cheeses that work well in this delicacy, and too many other options to list here.
For the record, I like mine on sourdough bread, using American cheese with some mayo and grilled slightly crisped and sliced into two triangles.
Manero's offers a chorizo version of stuffed mushrooms that features baby cremini mushrooms, which are very flavorful. They're stuffed with chorizo, peppers, onions, breadcrumbs, and mozzarella cheese, drizzled with smoked paprika roasted red pepper gastrique.