Bap, Cob, Bun, Batch? Stuff and nonsense. Every body knows it's a Barm; as in "give us a donnoh, but stick it on a Barm". I don't eat many Chip Butties a year but when I do, it must be white bread and Anchor Butter (in sufficiant quantities to make the chips visible through the bread, after sqwoshing). All the best PP.