A Zen master was visiting London. He went up to a hot dog vendor and said, "Make me one with everything." 

The vendor fixed up a hot dog with fried onions, gherkins, and mustard and handed it to the Zen master, who paid with a £20 note. The vendor put the note in his register and snapped it shut.

"Excuse me, but where's my change?" asked the Zen master. 

"O my brother," said the vendor, "change comes from within."