What about a deep dish Mac & Cheese, let it cool, chill in fridge. Slice it into 1" slabs, egg dip and panko bread crumbs, very quick high fry & drain. This would give you a firm slab sandwich worthy with crunch and chew.
Now, what you dress the sandwich up with… thats another story. I’m really wondering what that could be.
My guess would be Yellow Mustard or Marinara Sauce like fried cheese. [;)][:p][8D]