Submitted by Andréa:
The joke is that he assumes the Burgers ‘n’ Things has a chef who’s such a prima donna (“prima donald”?) that he’d be offended by a customer adding ketchup?
B.A.: Is “deconstructed food” a thing? This seems to want to be an “artisanal food” joke, or better yet “Ordering a BLT at the restaurant in Ikea.”