It took me a minute to figure out what is meant by a "chip butty" -- I couldn't imaging it was anything made from okra, and had to look a bit further back in the thread.

It's a fried potato sandwich, right? (I do have enough international savvy to have learned that "chips" are what we call "fries" on this side of the Atlantic, and "crisps" are what we call "chips.") I had never encountered such a thing before arriving in New Orleans 30+ years ago, and did not know there was a British equivalent of this carbohydrate overdose.

The classic N.O. potato po-boy is basically an effort to duplicate the taste, and exceed the filling-ness, of the popular roast beef po-boy sandwich, without the expense of using actual meat. A liberal dose of roast beef gravy is the critical ingredient, which normally disqualifies the sandwich for vegetarians. My vegetarian guest figured he could ask the counterman to subsitute "red gravy" (tomato sauce) and came up with something he could eat, and indeed did eat with considerable gusto, once every day for over a week.