I've had a chip butty minus the butter as I do not like buttered bread. THey are incredibly filling, tasty and cheap as....well, chips! All Chippies will sell them. If you want to make it at home you need to do the chips british style ie triple cooked and use propper butter no the liquid stuff you guys seem to have. warm the butter so it spreads better. cut the chips into CHUNKY chips (no french fries here) parboil the chips in salted water, pat dry on kitchen paper, heat a fryer or chip pan to 140C, pop the chips in for 7-8 mins, remove from the oil and set aside, heat the oil to 180C pop them back in for three minutes, drain well and whack them in your bun (proper soft bap not the weirdly sweet stuff you have on your shelves) make sure to apply plenty salt and vinegar and optionally, add sauce of choice (normally ketchup or brown sauce).
It's surprisingly delicious.